Disclaimer: This is a guide for selecting non-merged units. This guide includes the collective wisdom of all builds and analyses on gamepress and gamepedia to the best of my knowledge. I am by no means an expert in this and only have used a fraction of the optimal builds, but the wonderfulness of FEH is that you can theorycraft. Inspired by the builds listed by /u/ardx and a desire to better understand what makes some units better than others. Technically this is more of a list of notable heroes for each common team role, given by the build, more so than it is a list of notable heroes for each build directly.

The goal is to win without losing any units.

• For Arena, you need to be able to counter meta units
• For Tempest, you need to be able to commit overkill on broken units

What are the possible ways to lose?

• There is an enemy unit with too high Def/Res to finish off before a follow-up attack or it would kill you with Vantage or Quick Riposte (QR).
  • Hector, Ryoma, etc.
  • Often paired with a healer.
• There is an enemy that you can not bait an attack from before they murder everyone.
  • Reinhardt, Bride Cordelia, etc.
  • Often paired with a dancer.

How do you avoid losing?

• You need a way to take out all defenders during the Player Phase (PP).
• You need a way to bait all attackers, and kill them during the Enemy Phase (EP).

PLAYER PHASE

Physical Nuke

• Role: One-round the enemy before they can hit you. The best units can do this to everyone except their specific counters and the worst should still be able to delete everyone they have advantage on. Some slow but bulky units will mix this with the QR Bruiser role to be useful in both phases. Falchion users can mix and match this with healer gimmicks. Should be paired with dancers and repositioning skills.
  • Red is often better used in simultaneous support or EP roles because the best blue and green PP dedicated attackers are simply better while red has more non-nuke options.
  • Any unit, especially bows, gains immense team support ability from Breaker skills as an alternative to Desperation.
  • Many blue builds use brave/firesweep lance with drag back or hit and run to implement MVK-style tactics that can be a powerful way for melee units to compare to ranged ones better in terms of safety.
• Brave/Killer/WoDao Sword (Atk/Spd)
  • No sword is as good at this solely role as their mage/spear/axe/bow counterparts due to range and movement options. Instead, swords will generally want to play at least one extra role. Most calculations will incrementally favor WoDao over Killer swords for damage but it is not really agreed upon how they stack up to Brave swords other than that all such builds can play this role well.
  • Hana (35/36) has the best offensive spread. Ryoma (34/35) and Lucina (34/36) are generally considered better overall characters though because their unique weapons allow them to simultaneously play other roles. Ogma (35/34), Lloyd (32/35), Marth (31/34), and CorrinM (32/32+) are outclassed but functional alternatives. Masked Marth (34/36) is identical to Lucina except for the lack of IVs.
  • Lon’qu (29/39), Athena (31/38), and Navarre (31/37) can attempt quad builds but they will generally be worse than optimal double builds. Karel (30/35) is too slow for Quad and too weak for Killer. Eirika (26/35) can also almost work but she is better off in a support role.
  • Lyn (28/37) with Sol Katti is a weird unique build because she can have Desperation with Brash Assault, a Breaker, or Vantage for Galeforce shenanigans.
  • Chrom (37/25) is also notable but his extra power does not always make up for the lack of movement. He can also play a QR role during EP. Alfonse (35), Gray (35), Laslow (35), Seliph (34), and Luke (34) are outclassed but comparable alternatives. Alfonse at least can get higher PP attack than Chrom when at low health.
  • Eldigan and Xander (both 32/24) are nearly identical except for their unique weapons. For PP, Eldigan is usually superior because he can run the Killer build off his weapon and can have a +Atk IV. Xander can also be better at using TA because he can pick it without sacrificing DC. However, horse Emblem will generally want to run mages so these are only better than other swords due to their movement and ability to play other roles. Cain (32/32) and Eliwood (31+Durandal/30), can also pretend to be relevant but their other roles are less useful. While Stahl (31/26) is not great for this role, it is still one of the only ones he can run at least mediocrely. In general, these horses are better in the EP, ironically losing the PP benefits of extra movement.
  • Zephiel (35/16) can do this but his lack of mobility severely cuts his PP options.
  • Draug (30/32) weirdly enough can actually aim for a quad build in armor emblem.
  • Palla (31/31) and Caeda (25/37) are all that Flier Emblem has in this role but they can even be outclassed vs. green by the far stronger green fliers.
• Brave/Firesweep Spear (Atk/Spd)
  • Cordelia (35/35) is the Hana of lances, where fliers reign. She is the only spear unit that can compare to the top swords in this role. Catria (31/34), Hinoka (35/32), and Est (35/30) are strictly worse but functional. Clair (26/36) can try for a quad build like Caeda but it is not great. Est also notably has ascended to memedom due to her potential to run Defense Ploy incrementally better than any other fliers due to her specific stat balance.
  • Bride Charlotte (36/32), Summer Robin (32/34), and Sharena (32/32) are functional but at least Sharena has some support options.
  • Camus (32/33) can be a blue Xander with his DC and mobility and lack of competition from an Eldigan, but he too is better off in EP roles. However, his worse defense and better speed make him more comparable to Cain and thus less optimal in QR roles, making him more reliant on filling this PP role than Xander/Eldigan. In fact, Roderick (31/34), Peri (33/33), and Abel (33/32) are very similar in this role despite being worse in others.
  • Ephraim (35/25) can actually play this role better than Eirika but he is still better off in a support role.
  • Effie (40/22) will destroy anything she touches…if she can actually touch it. She is often classified as significantly better than Zephiel because of her sheer overkill being on another level with far fewer counters.
  • Overall, the lack of speed in most of spear units makes them worse at this role than swords, except on Flier emblem, where they are far superior.
• Brave Axe
  • Legion (36/35) is the Hana of axes, even though fliers are generally better here. Raven (34/35) is also capable of competing with Cordelia and the top swords in stats but is strictly inferior. Spring Chrom (35/32) and Barst (33/32) also exist but speedy axe users are generally worse than slow ones due to the lack of Killer or firesweep axes.
  • Anna (29/38) is weird. She can quad and run her own weird builds because there is no one that really competes with her. However, lack of a killer/sweep weapon hurts her options compared to the myrmidons and Cordelia.
  • Summer Tiki (36/30) and Bartre (36/25) can play a Chrom-like role but are again outclassed by the fliers.
  • Frederick (35/25) stands out against the sword and lance horses with a slightly higher attack that makes him more comparable to the infantry and flier nukes. Gunter (32/24) is similar but suffers from being better in EP roles like most horses.
  • Cherche (38/25) is basically a flying green Effie and easily the best of the axe nukes thanks to her mobility and the lack of firesweep competitors (where speed matters more). Michalis (34/26) is also a comparable but inferior alternative that is solidly better than most non-flier greens but suffers from a lack of IVs.
  • Minerva (31/34) may often be considered the best flier, but not because of this role. She is a strange example of where being well-rounded and solid in many roles simultaneously is actually comparable to excelling at just one.
  • Hector (36/24) can cover this role like Zephiel and Effie do but his unique ability to be absolutely ridiculous in almost any combat situation makes better at flying into the enemy army without any expectation of being repositioned away from it after attacking, a luxury that almost no other unit has except for select Vantage+DC+Aether builds that rely on thinking numerous turns ahead. He still has DC and QR despite running Vantage, Wings of Mercy, or Wary Fighter at the same time, making him capable of unique B-skill builds like Lyn (RIP Eliwood).
• Brave/Firesweep Bow (Atk/Spd)
  • Bride Cordelia (35/35) is the Hana/Cordelia of ranged attacks. She can run double, brave, quad, firesweep, and even support roles better than nearly all other archers to an extent only her spear counterpart is capable of. She is not necessarily as solid in other roles as the swords or as brutal as Cherche/Effie, but she gets the job done with a colorless coverage that has almost no non-Raven counters.
  • Summer Gaius (30/37) can quad incrementally better but doble/firesweep builds are often better, cheaper, and more reliable than quad. Setsuna (28/37) used to be decent before Cordelia and Gaius invalidated her but she can at least be a functional alternative.
  • Takumi (32/33), Jeorge (32/32), Klein (31/33), and Leon (34/30) are almost identical and strictly inferior alternatives. Klein has the closest build by default (Death Blow and Brave Bow) but Takumi actually stands out by virtue of being able to play EP roles with his incrementally better bulk than the other two. Still, all four are extremely powerful units better than all but the best melee physical nukes.
  • Because ranged brave weapons are so much safer than melee ones, even lesser archers like Virion (31/31), Gordin (31/25), Faye (30/25), and Rebecca (29/34) can compete with decent melee nukes in the PP while simultaneously covering niche EP roles. These units are also quite strong with breaker skills, which effectively allow them to cover a color without penalty.
• Poison Dagger  (Atk/Spd)
  • Kagero (35/32) may not be relevant against non-infantry units and may struggle in Tempest Trials compared to brave/blade users due to lack of sheer power, but until infantry units stop being ubiquitous, she will be relevant. However, most of the Brave bows are still quite capable of destroying infantry and Kagero’s anti-mage/infantry role is more limited by Raven tomes, so she is at best an alternative than a competitor.
  • Gaius (29/36) and Saizo (29/34) can serve as a knockoff Kagero, but they will still be worse at this role than the less brave bows. Daggers, for the most part, are inferior nukes and should be used in debuff support roles.

Magical Nuke

• Role: Kill everything except anti-Mage builds. Slaughter them all with little to no regard for color. The gap between the better and worse units is almost large enough to contain all the physical nukes as the best magical nukes are superior in the PP to the best melee ones by a large margin and the worst are effectively unusable.
• Blade/Ragnarok (Atk/Spd)
  • Katarina and Tharja (32/34) are nearly identical with the former slightly better due to also having magical bulk and the latter having the blade by default.
  • Celica (32/33) is typically considered to be the best because Ragnarok allows her to play other roles better despite being worse than Tharja for blade past the first attack. Celica also has the luxury of enough power at full health to run Ragnarok with swordbreaker instead of Desperation to more reliably take out most enemies in the game without need for setup. Finally, she has the option of running Renewal to refresh her initial attack boost.
  • Sanaki (37/26) and Lilina (37/25) can also play this role but they are often unable to one-shot important units in Tempest/Arena due to lack of sheer overkill so they are better off in Raven roles. They work better with Quick Riposte + Raven tome, paired with Triangle Adept.
  • Due to the nature of horse buffs, Leo (29/22) can actually run a blade tome but he is much better in other roles and the other horse mages can cover green far better than him.
  • None of the other red mages have enough power and speed to compete.
• Brave/Blade/Aura (Atk/Spd)
  • Reinhardt (32/23) is superior to the blade tomes because he has no need for speed and his bulk allows him to play other roles. With QP Moonbow, he has almost no counter and can do by default what blade and quad builds require support and min-max builds to do. Since all magical nukes are nearly color-blind, he is strictly better than other color alternatives and can pair with any red support (not even necessarily a red nuke) to delete the entire cast.
  • Linde (35/36) is a comparable alternative that also is superior to other color builds due to her Hana-level stats and simultaneous healer options.
  • Delthea (36/34) is almost identical to Linde but slightly worse with a blade tome due to her higher attack not making up for her lower speed. However, she does have options with Dark Aura that can make her a support unit as good as or better than Linde depending on the specific context.
  • Olwen (26/34) can attempt a quad build but suffers the same limitations as other quad users. However, her speed also makes her a functional blade user, especially in horse emblem, where she can outshine even Reinhardt. Ursula (29/32) can also attempt the horse blade but is strictly inferior as speed is much more important than attack.
  • Summer CorrinF(31/34) has the nearly unique privilege of being a ranged flier, so she is almost immune to being attacked with appropriate positioning. In flier emblem, she can act as an ungodly combination of Olwen and Cordelia that easily make an argument for her being a top unit in the most meta-defining role.
  • Bride Caeda (29/37), Spring Lucina (29/36), and Mae (36/31) are all decent blade tomes but the first two would be better off attempting to quad if they could and the third is too slow to compare. While Linde is better than her red and blue rivals, these blue mages are not. Still, they can be quite functional alternatives.
  • RobinM (29/29) is far inferior to the others for blade usage but unlike the worst red tomes, he can actually implement it with buffs and unlike RobinF, he can make use of IVs. Still, he will not be better than other colors or spears, so there is little reason to use him for this role.
  • Odin can vaguely do this role but he is even worse at other roles so he deserves a mention here.
• Blade/Naga (Atk/Spd)
  • Nino (33/36) is effectively identical to Linde because 2 points of attack means nothing to blade tomes compared to what 2 points of speed would mean. She lacks other options besides niche anti mage roles but she is tied for the best color-blind blade nuke role. Still, Reinhardt can outclass her due to needing less support and gaining more from horse support.
  • Summer Elise (36/34) is almost identical to Nino but typically considered incrementally worse due to lower speed not being worth the attack boost when running a blade tome. Unlike Delthea or Celica, she does not have a unique legendary weapon option to consider as an alternative. 
  • Soren (33/33) has the ability to double almost every unit in the game with Life and Death Equipped. A plus speed boon takes him up to 40 and his weapon, although without any abilities, is strong in its own right. Like Celica, his strength is being able to nuke without buffs. His high res also allows him to work on EP even with Life and Death Equipped. Desperation (for TT) or Green tome breaker (for Arena) is a must.
  • Sonya (33/31) is also notable but even more clearly worse than Soren with a blade tome. She can however use her unique Wo Dao tome Dark Excalibur to run a non-blade build that is decent though often inferior.
  • Julia (35/26) is not nearly as good as Lilina/Sanaki at running an inferior blade tome, but that is not her purpose. Instead, she is capable of effectively running many non-nuke roles and countering dragons/Reinhardt, giving her many niches. However, as a pure PP nuke, she is inferior to Nino. 
  • Cecilia (32/25) at first appears to be a much slower and thus much worse version of Nino but her power scaling on horse emblem makes her terrifying. Still, blade users need speed more than attack, so while she is better than Leo, she is still worse than Olwen. Of course, there is no real competition for her spot on most horse teams as a non-blue unit, so she is quite capable.  
  • Spring Camilla (35/25) has the nearly unique privilege of being a ranged flier, so she is almost immune to being attacked with appropriate positioning. In flier emblem, her blade tome becomes the strongest but her raven build is arguably even better. Raven tomes are definitely powerful in the PP but I have decided to discuss them only in the EP section to avoid redundancy. 
• Wrathful Staff (Atk/Spd)
  • Elise (32/32) in horse emblem is the only really viable build due to lack of a blade staff, but she can serve this role similarly to a double Bride Cordelia while simultaneously covering healing. Linde and Falchions can also cover healing though, so her niche is not as secure as it might first appear. Without quad/blade, she lacks the overkill necessary to own at arena/tempest.
  • Priscilla (29/29) and Clarine (25/33) are also worth mention as alternatives.
  • Genny (35/25) and Lucius (32/30) are notable but their lack of horse buffs and speed keep them far away from approaching overkill.

Support

• Role: Heal/buff allies, move allies around, chip/debuff enemies, and/or poke at the rare unit that they specifically hard counter via gem units or killer specials. The best of these will rarely be attacking but when they do, they should be able to delete at least one class of targets. Technically any build can double as a support build with reposition, C-skills, and seals, so it is rarely necessary to have this covered. It only makes sense to include a supporter if they are better than just having a duplicate of another unit. If they hard-counter one class of units, it should be whatever class the rest of your team has trouble with.

• Dancer
  • Olivia and Azura can cover green and red respectively with gem weapons or triangle adept. They can also abuse breaker skills but will typically be better off with Wings of Mercy.
  • Ninian is functional on dragon teams with triangle adept, but is worse in general due to almost unusable attack and her DC weapon being more usable in EP compared to PP use of gem weapons.
  •  It is also worth note that units with draw back and reposition can act as pseudo dancers when assisting in retreating from attacks, but they still lack the pure offensive potential that dancers allow high mobility (horse/flier) units to clean the map regardless of layout.
• Stat Boosts
  • Eirika and Ephraim have unique weapons that let them buff up to 4 stats with full skills/rally assist, and they can serve niche PP/EP roles simultaneously, but they lose out on optimal buffs (sword is only +3 not 4 Atk) and repositioning skills are almost always more useful than rally ones. Furthermore, seals allow anyone to become at least a partial buff for blade infantry and the best PP attackers (Reinhardt and Bride Cordelia) do not even need buffs.
  • Any flier/horse/armor/dragon will be better at this than the Sacred Stones infantry as they can simultaneously buff just as well as an afterthought.
• Falchion Medic
  • Lucina is generally considered the best because speed is weirdly more important than HP/Def/Res for taking hits. Marth can also work if speed is not enough and Masked Marth is strictly inferior to Lucina and Alm is to Marth.
  • Chrom is the only other Falchion that can rival Lucina, primarily due to his far higher HP and defense allowing him to play other simultaneous roles better.
  • Anyone with Renewal can also also cover this role, but they will be worse at it. 
• Healer
  • This is more of a function of the assist than it is of the healer in PP. In EP, healers like Azama stand out with Martyr though.
  • Rehabilitate is generally considered to be the best if your units somehow survive hits and gets the best speed in Tempest Trials.
  • Recover is also functional alternative for fixing Raven, QR, and other EP units.
  • Physic is nice for minor heals on PP units that can only soft counter certain EP threats when above a certain HP threshold without giving up positioning.
  • Absorb is at best a funky gimmick with Elise in horse emblem.
• Chip/Debuff
  • Gimmicks with daggers, Dazzling Staff, Poison Strike, Savage Blow, Pain, Slow, Ploys, and so forth are unfortunately underpowered in the current meta because a unit that does not one-shot another on its turn effectively wastes its turn and often makes enemy units even more dangerous. 
  • Ideally, this could be used to handle boost/ploy/etc units that rely on high HP but the meta has yet to develop these as relevant.

ENEMY PHASE

Vantage

• Role: Kill the enemy before they can kill you before you can kill them. Often a win condition near the end of the battle and one of the most dangerous builds in arena defense. For arena offense and Tempest Trials, it can make a single unit clear up a map with proper setup. The best of these units will be able to get to the HP range safely and then dole out a single powerful attack that should be able to one-shot all who could have one-shotted them. Those who can not reliably kill multiple colors in a single hit but can tank hits from multiple colors should run a QR build instead. However, the best vantage units are actually those that are useful in other roles before vantage is even active. All vantage units will want Close/Distant counter.
• Swords (Atk)
  • Ryoma (34) and Ike (35) are great at this because they can run it while simultaneously being a PP threat. Ryoma is better at attacking as well due to his speed while Ike is better at setting up vantage due to his defense. These builds can also perform healing roles by sacrificing their Aether-gained health to allies in exchange for returning to Vantage range.
  • Lucina (34) and others can compete by using Distant Counter but sacrifice the stat boosts of Fury, which synergize well with vantage.
  • Chrom (37) is potentially notable because his attack does not need Fury but his healing synergy is still trickier to pull off than just staying at low health. On paper, his healing might be able to surpass the Aether-vantage synergy of Ike but he is unable to take full advantage of it without both Heavy Blade and Distant Counter.
  • Eldigan and Xander (32) are also capable of competing as the former does not need Heavy blade and the latter does not need Distant Counter, and horse boosts make them stronger than other swords. While heavy blade or fury is arguably better than a killer weapon, Xander also lacks IVs, so it is difficult to determine who is better. 
  • Zephiel (35) is also decent at this but his inability to run Wary Fighter or Quick Riposte with Vantage simultaneously limits his potential.
• Spears
  • Cordelia (35) can do it but she lacks distant counter and neither brave nor sweep are functional with vantage, preventing her from playing multiple roles like the swords can. The other pegasus knights suffer the same limitation.
  • Ephraim (35) is surprisingly good at this because his other role (buff support) and low speed do not get in the way. Sharena (32) is similar but lacks IVs and the rest of the spears lack unique weapons. Bride Charlotte (36), Donnel (35), and Summer Robin (32) also work but are not really worth it compared to other roles.
  • Camus (32) is identical to Xander except for how best he gets his health down, unless he runs Fury. Unlike Eldigan/Xander, Camus is more limited to this role over walling physical hits.
  • Effie (40) again surpasses Zephiel in relevancy through sheer attack numbers, though she still has many similar limitations and lack of a good EP weapon.
• Axes (Atk)
  • Legion (36) functions much like all the others with high attack and no DC weapon. Summer Tiki (36), Bartre (36), Spring Chrom (35), Raven (34) and Barst (33) are the other notables.
  • Cherche (38) is probably the best axe for this and again makes the infantry outclassed due to flier buffs. Still, her lack of a DC weapon makes it difficult for her to play multiple roles.
  • Frederick (35) has much the same difficulties of Cherche and other horses but at least has higher attack than Xander/Camus to make up for his lack of unique might 16 weapon. Still, without Fury, he has trouble setting up.
  • Hector (36) is simply overpowered at too many roles at once. Unlike others who lack a DC weapon, he has no real need for Fury thanks to Armor unit BSTs and thanks to having a unique B-slot weapon, he can pull off builds that other armors can not. Between Armands and Vantage, he is perpetually deadly and capable of playing nearly every major role a team could need simultaneously, without needing setup. On defense teams he is relatively non-threatening but only if you pay close attention to his B-slot and strategize around it and on offense teams his lack of speed is not a problem since you can just throw him into the middle of the enemy army. Still, he does have limitation in Tempest Trials, where turn count is paramount and he becomes inferior to units with higher movement speed.
• Dragons (Atk)
  • Adult Tiki (35), Nowi (34), and Fae (33) all have DC weapons (Fae though inheritance) and solid attack but their weapons are lower might and magical. Normally magic attacks are better for damage because most units have lower resistance on average but the sweet spot of low HP with low Def/Res that vantage builds hope to take adVantage of  is primarily present in units like blade mages and quad strikers, who fall more easily to physical attacks. Other units are better eliminated during the PP or by EP QR tanks while vantage serves more of a niche for taking out units that even heavy QR walls can not block. Dragons also usually have excellent bulk in all defensive stats, so they are better able to take on QR or Breaker roles. 
• Tomes (Atk)
  • Sanaki and Lilina (37) are probably the best for this with default or blade tomes, but they rely heavily on support setups to deal enough damage for reasons similar to why dragons are limited.
  • Mae (36) is probably the only blue tome who is better at this than she is at a Desperation build and can actually use either Owl or Blade tomes for it. She also stands out better from the red and green vantage mages due to having less competition from spears.
  • Julia (35) is also capable, especially on dragons who can be especially dangerous late-battle opponents.
• Colorless (Atk)
  • Kagero (35) can do it on infantry but no one else is really relevant.
  • Takumi (32) can actually run this somewhat well due to his balance between bulk and power being perfect for causing the most units the most trouble, but in the end no bow unit is really going to be able to do and receive enough damage to make a vantage build sustainable, especially since most will be running brave or firesweep bow.
  • The clerics can not do Vantage builds because Wrathful Staff is also the B-slot.

QR/Breaker Tank 

• Role: Bait the attack of an enemy and kill them in the counterattack. Accomplish this with QR, DC, Breaker, seal, and/or threaten skills. Gem weapons and Triangle Adept (TA) are better used on Walls than tanks because tanks are intended to take on multiple colors. The best tanks will kill anyone who attacks them, taking little to no damage from those they counter and only moderate damage from everyone else except their counters. While they often become useless after their first few interactions, they are absolutely essential to beginning a fight without losing anyone, as the player will more often than not always have to tank at least one enemy attack (or sometimes multiple in grand hero battles). It is also worth note that Quickened Pulse can make units with low attack but high defenses absolutely terrifying in counterattack with QR immediately activating Bonfire on counter and Glacies on follow-up. 
• Anti-Sword/Axe (Atk/Spd/Def)
  • Ike (35/31/32) can generally take on any sword or axe unit with any weapon, allowing Ragnell to cover a number of other roles. He is also well-built for heavy blade and Aether, which allows him to tank through countless units where most tanks would only be able to handle a couple before needing to be healed. This Ike can even mimic Falchion builds in Tempest Trials by constantly healing himself. Generally speaking, Aether is better than Galeforce for tanks.
  • Ryoma (34/35/26) is better at taking hits from mid-speed swords than Ike but is otherwise inferior due to his lower HP, attack, and defense. He is more likely to handle mages and be a general wall to all units but Ike is more reliable at countering the >50% of all units he handles. The other speedy Myrmidons suffer similar and worse limitations due to lack of distant counter.
  • Lucina (34/35/25) also has speed and healing to make up for her defense, and she can even surpass Ike at using heavy blade Aether against melee opponent. Marth (31/34/29) is similar but arguably worse again, because FEH favors offense over defense, even on the defense. Alm (33/30/28) is even worse for the same reasons.
  • Eirika (26/35/26) can vaguely function in this role but is not really favored against enough swords, even with swordbreaker, because her high speed does not gain as much from swordbreaker as Ephraim’s does from lancebreaker.
  • Chrom (37/25/31) can almost outperform Ike due to his greater HP and Falchion healing like Lucina but his durability suffers from his lack of speed and distant counter. However, clever positioning and tactics can actually allow him to use taking extra hits to his advantage, charging Aether faster and giving him more durability against teams with more melee and less ranged.
  • Gray (35/32/30) suffers from lack of a unique weapon but he is strictly better than most other competitors for this role.
  • Seliph (34/24/30+Tyrfing), Laslow (35/26/30), Alfonse (35/25/32), Hinata (32/24/36), Luke (34/28/30), and Stahl (31/26/30) function with this build so they are also worth note. Unfortunately, their two roles (Red Physical PP and Anti-Sword/Axe EP) are irreconcilable because their best weapons for PP (brave) are their worst for EP (gem/silver) and they lack reliable healing to reuse QR/Breaker.
  • Xander (32/24/37) and Eldigan (32/24/34) are again decent at this for the same reasons as their other builds, but they are often better in those roles, since extra movement makes almost no difference for non-armor tanks.
  • Draug (30/32/39) is also pretty decent at this though he is better as a wall due to his low damage output and high speed.
  • Zephiel (35/16/38) plays this role pretty optimally with any of QR, Breaker, and Wary Fighter.
• Anti-Spear/Sword (Atk/Spd/Def)
  • Cordelia (35/35/22) and others lack the DC and healing potential of swords but they can abuse Galeforce to tank their way through an entire army. However, it is difficult to determine which of the Pegasus knights are best for this because at least some bulk is necessary to pull it off but the optimization problem between all four stats and A/B slots is too complicated to make clear distinctions. 
  • Catria (31/34/29), for example, is possibly a good middle ground. It often makes sense to select a spear tank who will perform other roles excellently and this one adequately. Again, the lack of unique weapons, specifically DC weapons, makes spear users suffer.
  • Subaki (25/35/35) is the extreme at the other end from Cordelia, but he is generally better as a wall.
  • Ephraim (35/25/32) is again notable due to his ability to cover his low speed with QR/Breaker and take advantage of his decent defense while simultaneously playing other roles, much like how he was able to multitask with vantage. Donnel (35/29/32) is a moderately bulkier tank that can survive longer but his lack of unique weapon makes him suffer. Bride Charlotte (36/32/24), Sharena (32/32/29+), and Summer Robin (32/34/28) are inferior but functional, and can perform this role alongside the PP nuke role much like the mediocre swords. Much like their sword counterparts, they can not do both optimally due to brave weapons being best for PP and worst for EP.
  • Lukas (35/22/38) is  potentially the best spear for this as his QR Bonfire/Ignis form his combined attack and defense stat easily makes up for his lack of a unique weapon. Most other walls have too low attack or movement to be functional tanks. Oboro (32/26/35) is a decent alternative.
  • Camus (32/33/31) is okay at this but his lower defense makes him worse Xander in protracted exchanges. 
  • Effie (40/22/33) may not be as good a wall as most armors but she is definitely one of the best duelists with any of QR, Breaker, and Wary Fighter. Gwendolyn (30/24/38) is functional but better as a wall.
• Anti-Axe/Spear (Atk/Spd/Def)
  • Cherche (38/25/32) and the other Wyverns are more suited for this than the Pegasi were due to having higher defense instead of speed. However, she still suffers from brave weapons being good in PP  and not EP, meaning she can only be optimized for one role.
  • Michalis (34/26/35) is technically better than Cherche at being a tank because his unique weapon gives him comparable attack and better damage output on defense. He also has better survivability, and can make do with DC or heavy blade fairly well to be a flying Hector or Ike. Beruka (29/23/37) is also worth note as a tank with a killer weapon but is better as a wall. 
  • Minerva (31/33/32) may not be as terrifying when attacking as the other Wyverns, but she is perhaps the best tank due to her well balanced stats and killer weapon. She is even capable of taking some minor magical hits for DC usage and has a one point higher BST than Michalis. However, her best build is actually based on Fury, Drag Back, and flier boosts, allowing her to simultaneously cover PP attack+support, and EP tank+wall roles better than any other Wyvern rider and most other units. However, outside of flier boosts, she is fundamentally just another melee unit with lower stats than the specialists of each role. Camilla (30/32/28) and Narcian (29/29/32) also work as far inferior alternatives to Minerva.
  • Frederick (35/25/36) is a slightly stronger Michalis/Hector on a horse without a unique weapon. Unfortunately, that lack alone is enough to put him behind them and his DC horse brethren in most cases, but he is probably still the best green unit in horse emblem when Cecilia is not present.
  • Legion (36/35/22) and the other fast axes lack bulk to properly due without unique weapons while Bartre (36/25/33) and other bulky axes lack speed and sheer defense to survive most attackers while suffering the same brave weapon conundrum. Not to mention that their movement is completely inferior to that of the Wyverns.
  • Hector (36/24/37) is once again absolutely broken here because he automatically has QR form Armads and can choose any other B-skill. In fact, just by having Armads, Hector is one of the best axe tanks and can build himself to fit any other role optimally without losing his effectiveness as a tank.
  • Sheena (30/25/36) is also worth note here as she is one of the only units who can serve as both a physical and magic tank at once. Though she is a bit weak, a killer weapon can make up for that since she is not usually trying to be a brave axe PP attacker at the same time. She requires distant counter and QR/Breaker is not much better than Wary Fighter.
• Anti-Colorless (Atk/Spd/Def)
  • Any armor with DC and >35 defense can handle all but the quad bows. Without DC, they stand no chance. However, this is not much different from their roles described above, with Hector dominating and Effie less relevant (due to lack of defense and overkill attack removing her main advantage over other armors). Instead, Raven tomes are often the best specifically colorless check as with Triangle Adept they are able to tank a great number of enemy units.
  • RobinM (29/29/29) is the quintessential raven tank. Between swordbreaker and triangle adept, he can handle over half the units in the game despite his mediocre stats, even in Tempest Trials. However, he must also be treated with delicacy befitting a blade tome user as he can not take any hits from green units. RobinF (29/29/29) is comparable but suffers from lack of IVs and the fact that there are far fewer blue than red units. 
  • Lilina (37/25/19) and Sanaki (37/26/17) can run raven builds quite well but their low defense gives them trouble against brave archers. Sophia (33/19/28) can handle them but she will almost always get quad-hit. Henry (23/22/32) can also try to tank well but his attack is too low to do any real damage without being a wall. Raigh (32/29/22) is between and with IVs can be comparable to RobinF, but his bulk is not quite optimal. Leo (29/22/25) probably gets the job done best but only on horse teams. Still, the lack of green units means that the red raven iche is not as strong as the blue or even the green.
  • Spring Camilla (35/25/30) is currently one of the only flying tome unit in the game. With Gronnraven and TA3 she can be a decent anti-colorless unit. Despite being a flying unit and taking 1.5x damage from bow units, TA/raven combination cancels out the weapon advantage and effectiveness disadvantage, making her only takes 0.9x damage from bow, even without Iote’s Shield. Her remarkable defense for a flier and mage makes this even more pivotal.  Quick Riposte then allows her to hit the enemy twice, effectively bait and ORKO any colorless unit, except opponent with Firesweep bow. This makes her arguably the best TA focused unit and the only one capable of compensating for a color weakness by handling colorless as well.
  • Summer CorrinF (31/34/22) can also run a raven build, but she lacks the durability that Spring Camilla has and will not be able to counter archers as well as the role would like. Instead, she is better off in a PP role with a blade tome. Still, her mobility options can make her invincible in the EP under the right circumstances, so she is at least better than the blue horse mages.
  • Spring Lucina (29/36/22) is better than Bridal Caeda (29/37/19) but still does not have quite enough defense to be better than RobinM. Odin (22/32/25) simply has an unusable attack stat. This leaves Reinhardt (32/23/27) to actually be one of the better RobinM alternatives but he horrendously wasted with a raven tome. Still, horse buffs can make him better than Robin. Due to all of this, RobinM is still a powerful niche tank if not optimal.
  • Merric (26/32/28) is somewhat functional and can be better than RobinF with the right IVs. Cecilia (32/25/22) also works well on horse teams, though her defense is a bit low and most horse teams buff offense before defense. Unfortunately, many of these builds still fail to defend against ubiquitous blue units like Reinhardt, making it often necessary to have a second green unit or dedicated antimage to cover that. Wolf tomes are an option but they tend to be insufficient as well.
• Martyr Healer (Atk/Spd/Def)
  • Azama (21/26/32) is the best candidate for physical tanking and one of the only healers that can be sent to the front lines in order to become reliably better at healing.
  • Lissa (26/25/28) is also notable for her relatively high combination of defense and resistance.

Anti-Meta

Ranged Anti-Mage

• Role: Unlike melee nukes and even all but the most aggressive quad nukes, magic nukes typically deal significantly more damage. This is partially due to the double counting of buffs with blade tomes and partially due to the fact that the units with high resistance often have lower attack than those with high defense, making them unable to perform their role despite the low defenses of most mages. However, it is almost necessary to have anti-mage units to counter Reinhardt and horse emblem in arena because there is often little opportunity to choose who to bait when horse mages can cover almost the entire stage on the first turn. Even vantage builds can not check openings because they need time to reduce their health. 
• Colorless Anti-Mage (Atk/Spd/Res)
  • Wrys (24/23/36) has the best resistance in the game but a horrible counterattack.  Mist (27/28/34), Serra (30/31/33), Priscilla (29/29/32), and Maria (27/34/32) are in a similar predicament. Also, all colorless units have trouble with raven mages.
  • Lucius (32/30/35), Genny (35/25/34), Elise (32/32/32), and are better with a wrathful staff but still too weak to get through the relatively high resistance of most mages.
  • Felicia (23/37/35) and Niles (25/34/34) lack attack power but can rely on Glacies to deal enough damage on the counterattack to clean out mages. However, the amount of prep necessary to set her up makes it difficult for her to be useful when she is most needed, in the first turns. Ironically, these units are excellent counters when used by the computer in Tempest Trials because the inflated HP means they can survive the mage opening and their inflated attack can actually finish the mages off on counter.
  • Kagero (35/32/28) is great for taking out infantry mages but still can not really hold her own against Reinhardt and horse blades due to her low HP.
  • Faye (30/25/31) can actually do damage but not necessarily enough to take out mages before their second attack strikes. Without Wary Fighter, the best Faye can do is use tomebreaker to counter a decent subset of mages. However, she does have ironic niche potential as a well-rounded unit (despite the fact most nich units are min/max) as she is capable of tanking hits from and raking down key meta threats like Reinhardt and Bridal Cordelia. 
• Mage Anti-Mage (Atk/Spd/Res)
  • Katarina (32/34/32) is able to use her A slot for something other than DC and has better speed than Sanaki (37/26/34) and Lilina (37/25/31) with still enough attack to take down most non-blue mages. Summer Leo (32/27/35)  is similar as well. Unfortunately, blue mages are the most dangerous. 
  • Leo (29/22/30) is also worth note due to his potential with horse buffs. Brynhildr’s ability to slow anyone he does not kill is actually quite useful at preventing sweeps. Between Draw Back positioning support and the potential to win many matchups, he is quite capable of performing multiple defensive roles simultaneously.
  • Bride Caeda (29/37/30) and Ursula (29/32/30) are passable blue anti-mage units.
  • Mae (36/31/30) Has enough speed that she won’t often get doubled, great attack, and good res, all of which can be boosted through her base kit’s owl tome. Red mages aren’t meta at the moment, but if that changes, she’ll find her niche. 
  • Julia (35/26/32) is great at covering blue mages and dragons but still has some risk with red ones. Fortunately, red mages are the least ubiquitous at the moment due to the competition of the red slot for support and physical DC roles. Sonya (33/31/32) is a comparable alternative who can actually benefit from her higher speed, depending exactly who she is up against. However, her unique weapon is somewhat awkward in this build though decent with QR.
• Melee Anti-Mage (Atk/Spd/Res)
  • In theory, one can give DC to any melee unit to allow their physical attacks to crush mages. There are a number of physical units with very high res, yet we also observe that these units are typically the lowest on tier lists. This is because they are often unable to kill on their retaliation and otherwise have terrible stats that prevent them from serving any role other than countering mages of at best two colors. There are however a few exceptions.
  • Florina (29/27/34), Caeda (25/37/34), Clair (26/36/33), Camilla (30/32/31), and other fliers have decent resistance but their lack of a DC weapon make sit difficult for them to play this role while also trying to quad as well. Again, a unit can not attack (brave/sweep) and counterattack at the same time.
  • Est (35/30/32) is actually capable of sending meaningful damage back at mages of all colors.
  • Eliwood (31/30/32), Fir (25/36/31), Lloyd (32/35/30), and Roy (30/31/28+) are passable with DC but are outclassed by the red mages in utility. They are still taken down by blue mages, though they can sometimes survive thanks to their speed.
  • Sheena (30//25/33) actually has higher defense than resistance but her HP and lack of decent competitors makes her capable of taking out non-red mages on counter, especially with Wary Fighter or Quick Riposte. Hawkeye (33/30) is similar but this is really all he is good for and is otherwise inferior to Sheena.
  • Titania (28/34/30) is an excellent counter with DC and QR/Breaker, especially on horse teams, and is capable of performing other roles as well.
  • Believe it or not, Hector (36/24/19) can actually handle non-red mages fairly well, through sheer quantity of HP and optionally wary fighter.
  • Mathilda (29/32/34) can perform similarly to Felicia/Niles with DC but he has even less utility beyond this niche. Jagen (27/24/35) is strictly worse than her.
• Dragons (Atk/Spd/Res)
  • Dragons generally have strange well-balanced stats and availability to DC magic weapons that make them fill most roles to a functional degree. Many have their own builds but the general two classes are TA/Breaker and Fury/QR. Both are also functional anti-mage and anti-armor builds that can tank most offensive units at least once and will win most duels. Their primary weakness however is difficulty in finding a team spot over more specialized builds and the fact that their main counters (Julia and Falchion) have numerous other uses, making most teams have a dragon counter without dedicating anyone primary or even secondary role to it.
  • Young Tiki (31/30/29) is basically a magic DC sword with no low stats. When played well, she can effectively defeat every unit on the enemy team alone. Like most dragons, she does best with sheer stats, but this guide focuses on unmerged unit builds and facing enemies with far greater stats (TT/GHB/arena) so she lacks the min-max necessary to compete with the best mages and tanks.
  • Adult Tiki is inferior to Young Tiki in both builds because her more extreme stats are still not high enough and her low speed is a huge weakness. She does well with non-dragon builds though, like vantage, and is still better than most red sword tanks at tanking.
  • Nowi (34/27/27) has stats tilted in just the right manner to make her dangerous in almost any role. With TA/Breaker, she can beat nearly any sword and lance, even Falchions, and she is still not even hard countered by mages. Additionally, due to the lack of a DC spear beyond Camus, there are fewer competitors in her color than others.
  • Ninian can actually run dragon builds functionally, especially on dragon teams, but otherwise she is inferior to all dragons and Olivia/Azura.
  • CorrinF is, alongside Anna and Spring Camilla, one of the strangest and most unique units. Unfortunately, her best builds are inferior to the dragon builds in nearly every way but she does serve a niche role team support that Nowi can do almost as well. Like Adult Tiki and Nowi, her stats are also lower than those of the better dragons.
  • Fae (33/28/30) is perhaps the easiest dragon to counter due to her color but she is also the best anti-mage dragon, checking Reinhardt and Linde better than the other dragons check their less dangerous and less ubiquitous threats. However, her lack of physical bulk means that she has trouble trading with melee units, making her a worse general tank.

True Wall

• Role: Highly situational and difficult to use units that give up the ability to trade hits with the enemy in favor of waiting for a special to charge. These units rarely function in the current meta because of how much more powerful offense is than defense. Defenders need every single stat in order to live (even attack) while attackers often only need attack and sometimes speed. Furthermore, walls are punished in arena/GHB where one can not risk losing a unit and in Tempest Trials, where one must complete maps as quickly as possible. And even more on top of that, the situation where no enemy unit can harm your remaining units is even harder than setting up a vantage win condition because not only do all your units have to take 0 damage, but they must also be able to actually damage all enemy units, which can often fall apart if they have just a single wall of their own. The only redeeming traits of walls are in TT when you need to tank a hit from a unit with ridiculous stats and your normal tanks would die, in GHB when constructing an MVK-esque strategy to win in a clever manner, or in arena where defensive tiles can actually make units into functional walls.
• Anti-Mage
  • There is no such thing as an anti-magic wall. The best you can get in a world where blade tomes exist is a tank or vantage unit. Clever positioning with panic powers can also work but even defensive tiles are not enough to reduce damage to zero. Fortunately, tanking is often all you need to take down mages because of their low bulk. 
• Color-blind Physical (Def)
  • Nearly any unit can be built with gem weapons, Fury, triangle adept, Wolf/Raven/Owl tomes, and/or breaker skills to shut down a specific color. Many units with very poor stats are only really good for this purpose and their stats are usually very low because they are supposed to be walls, so it works out.
  • Draug (39) also has 32 speed, making him effectively immune to all axes when built for that purpose as they will often not even be able to double him and he can double or even quad back to quickly get off Bonfire/Ignis with a killer weapon. Unfortunately, there is not much point in this build if all it takes is a single magical unit to one-round it. Zephiel (38) trades speed for attack and can also be functional, but he stands out better in other roles. Hinata (36) is similar to a red Lukas, but with worse stats in general.
  • Xander (37) and Eldigan (34) once again are comparable with IVs, and their extra movement and horse buff potential makes them promising alternatives to Draug.
  • Lukas (38) can sacrifice his attack for defense with Fortress defense to make even the strongest axes have trouble hurting him. He does not have the option for Wary Fighter and has lower HP than armor units, but his movement speed and equivalent attack easily makes up for it. Oboro (35) is a passable alternative. Seliph (34+Tyrfing) does well below 50% HP thanks to synergy with Tyrfing and Defiant Defense, but he still has trouble comparing to Lukas. He is also notable with Brash Assault.
  • Subaki (35) is effectively a flying blue Draug, but with an even more abysmal attack that makes him incapable of finishing enemies off without a single color focus. Since this category is for general physical walls, he makes more sense as a general red color wall for his ability to survive red magic better than Lukas.
  • Michalis (35) is a flying green Lukas with a unique killer weapon, which is the most important type for physical walls. Beruka (37) has all the benefits of Lukas and more from being a flier, but she lacks attack. Frederick (36) is once again notable but his lack of unique weapon makes him inferior to other axe options.
  • Hector (37) is Hector. Still. Nothing has changed here.
  • Azama (32) stands out among healers as having high enough defense to be notable as a wall but in reality he often ends up as a regenerating Martyr tank with Pain chip damage but no killing potential.
• Close Counter Mages (Def)
  • Henry (32) has strange potential to stand in the way of enemy units and return fire with Ignis/Bonfire and Poison Strike but his lack of ability to properly finish off units quickly makes him quite similar to Pain Azama.
  • Boey (32) and to a lesser extent Merric (28) can both attempt to wall blue units but they are generally outclassed.
  • Spring Camilla (30) effectively becomes a flying ranged Hector with CC and a Raven tome and is quite capable of being built to be a wall as well as a tank.
  • RobinM and RobinF (29) are also quite capable of being true walls while still having the offensive/retaliation ability of a tank. TA RobinM is generally considered to be better though because he can cover more units (far more reds than blues), he has IVs available, and he is not outclassed (as there are no truly defensive blue mages).
• Single Color Universal (Def/Res)
  • Some units can passably tank magical attacks while walling physical attacks.
  • Young Tiki (32/29) is probably the best universal single-color dragon but she is better off as a tank.
  • Nowi (27/27) with TA and sword/lancer Breaker can cover all red and/or most blue units, but she is generally better off as a tank than a wall.
  • Gwendolyn (38/28) faces down almost any unit at least once or twice and return fire with killer specials, but her lack of speed makes her extra bulk relatively irrelevant without Wary Fighter, which costs her QR/breaker.
  • Subaki (35/22) is a weaker but more mobile Gwendolyn with better potential for QR/Breaker and is probably the purely red non-dragon counter to both physical and magical damage.
  • Sheena (36/33) is the closest thing to a true universal wall with Wary Fighter.
• Whale Armor
  • A fully optimized and whaled armor emblem team on defensive tiles is arguably the strongest possible team in PvP and the upper echelons of arena, but this guide does not consider merges, so armor teams will typically be matched against merged horse mage teams and get obliterated.

THOUGHTS ON TIERS

Tiers are fun. Sorting them is like playing FEH, solving a puzzle to victory. They are also a nice way to quickly demonstrate the results of analysis and are a nice easy reference for discussion. This list assumes no merging, unlimited inheritance, and the state of the meta c. July 4th, 2017. It is divided into two lists: Player Phase and Enemy Phase, and designed for analyzing who the best options for TT, Arena, and GHBs are. A general tier list that demonstrates how good units are in both PP and EP would look very similar to the “official lists. Here, I have split the faster and slower swords red units apart for visualization purposes.

Player Phase Tiers

S Tier: Will delete all but a few units without taking any damage and can be reliably expected to wipe one to two enemy units every turn with support (stats and/or dancer) without any risk of retaliation. Outclassed by no one.

A Tier: Expected to take out at least one unit every round, regardless of color, except for soft counters and TT/GHB units or tanks on defensive tiles. Might have some risk of counterattacks but can handle them. Outclassed by at least one other unit or build.

B Tier: Capable of taking down enemies of at least two colors with support but lacks the overkill necessary to beat more than one color if their HP is inflated. Likely requires some support to reposition. Could be A tier if not outclassed.

C Tier: At best capable of one-rounding a single target enemy unit with support. Completely blocked by dedicated walls. Heavily outclassed or relies on a strange ineffective build.

D Tier: Walled out by dedicated tanks and all relevant walls. Still outclasses some units.

F Tier: Incapable of defeating enemy units without at least two rounds for a special proc.

S
A
B
C
D

Enemy Phase Tiers

S Tier: Immune to all but a few select counters and deletes most of them on the counter. With support that can eliminate their counters, they are effectively unkillable. Outclassed by no one.

A Tier: Has a winning matchup with most units, and goes even with those that have color advantage on them. Solid against both magical and physical attacks. Outclassed by at least one other unit or build.

B Tier: Capable of tanking and dueling two or more combinations of color and physical/magic damage while returning fire, or will of wall out at least two colors long enough to win after a couple rounds. Could be A tier if not outclassed.

C Tier: Can wall out at least one type of unit and tank at least two with support. Still prone to losing duels to dedicated attackers of the same color, but that is someone else’s responsibility. Heavily outclassed or relies on a strange ineffective build.

D Tier: Only useful for tanking units of the the target color, of either physical or magic damage. Can wall a single type of unit under special circumstances but will not be guaranteed to kill in the counter. Still outclasses some units.

F Tier: Incapable of surviving attacks from any class of units or can survive one or two rounds with the target color without returning substantial damage.

S
A
B
C
D