Superheroes are the stuff of legend, and some heroes are born powerful while others must work hard to build their abilities and gadgets. In My Hero Academia, quirks are the norm, and these quirks are just as useful for villainy as heroism, and Stain the hero-killer has a deadly quirk. If he ingests someone's blood, he can render them paralyzed, then finish them off.
Cool characters like Stain are fun to pit against fighters from other anime series, and this time, Stain is going to face off against the characters of Fullmetal Alchemist: Brotherhood. It's an anime where alchemy and homunculi are possible, and Stain can defeat some of these characters... but not others.
10 Can Defeat: Edward Elric
This won't be easy by any stretch, but Stain could pull it off sooner or later. Edward is a nimble martial artist, having trained under Izumi Curtis, and he can combine that with his advanced alchemy skills during a duel.
Edward can hold off Stain for some time, but he'll get tired, and Stain is faster than Ed. One little cut is all it takes to win, since Ed will be rendered helpless once Stain ingests his blood and paralyzed him. Assuming that Ed doesn't have a Philosopher's Stone on him, that is.
9 Can't Defeat: Greed
Greed is one of the seven homunculi that was created from Father, and he is roughly in the pack's middle where sheer combat strength is concerned. He has some martial arts skills and can harden his skin with carbon, tough like a diamond.
In a duel, Greed can harden his skin from head to toe like that, and thus Stain has no way to cut him and draw blood. Regular swords and knives aren't enough to beach Greed's skin, so Greed can wear down Stain or just convince him to leave. Stain wants easier targets than this.
8 Can Defeat: Lust
Here comes another homunculi, and her defenses aren't as tough as Greed's. Lust has the Ultimate Spear, meaning she can elongate her fingers into long points that can stab through absolutely anything (or use her fingers like swords).
That's scary, but Lust is too slow to actually stab Stain like that, and Stain can outmaneuver her on the battlefield. Once he gets a blood sample, he will completely paralyze Lust for a few moments, then use his knives to carve out her Philosopher's Stone and tear it right out.
7 Can't Defeat: Hohenheim
This fight would be over before it even began. Hohenheim is in a whole different league, being superior even to Father's seven homunculi. Hohenheim has vast knowledge of alchemy and the world, and his defenses are impeccable.
In fact, he doesn't even have to move to perform alchemy, so he'd throw Stain all over the battlefield without moving. If Stain did get a blood sample, that wouldn't help, since Hohenheim can still perform alchemy even if he's paralyzed.
6 Can Defeat: Lan Fan
This Xingese girl is a bodyguard of prince Ling's, and she is well-trained in the ways of tracking and melee combat. She and her grandfather Fu can even take on the Elric brothers if there isn't too much alchemy involved.
But that won't save her against Stain. Lan Fan and Stain move and fight at roughly the same level, but the difference is that Stain just has to draw a little blood to turn the tide in his favor. Just one shallow cut is all he needs to deal, and it's all over.
5 Can't Defeat: Roy Mustang
Roy Mustang is an alchemist like Edward, but he wields a wholly different kind of alchemy. He's known as the Flame Alchemist for a good reason, and his fire abilities are all thanks to Berthold Hawkeye.
With his right hand, Roy delivers powerful fireblasts at his enemies, and with his left, he can create much smaller reactions. He has been known to vaporize people's eyes or tongues like that, and he can do that against Stain, too. And unlike Envy, Stain can't regenerate his eyes. He's doomed.
4 Can Defeat: Alex Armstrong
Major Alex Louis Armstrong has a similar combat strategy as Edward Elric: to combine martial arts with sheer alchemy skills, and use them as one. Alex Armstrong is slower than Ed, but hits harder and has more experience.
This still won't save him from Stain, though. At some point during their duel, Stain will find a way around Amrstrong's barriers and alchemy projectiles and deal a shallow cut, and that blood sample will seal the deal. Armstrong isn't like Hohenheim; he can't perform alchemy while paralyzed.
3 Can't Defeat: Pride
Greed would be immune to Stain's attacks because of his hard skin; Pride would be immune because he does not have any blood to start with. Pride looks human in his Selim Bradley form, but it's really just a hollow container.
Pride's real body is a shadowy mass of tendrils, mouths, and eyes, and Stain has no means whatsoever of defeating such a creature via his quirk or his combat abilities. At best, Stain would realize this and flee, and hope that Pride can't catch him.
2 Can Defeat: Scar
A clear trend is emerging: these battles are largely based on whether or not Stain can obtain a blood sample from his enemy and paralyze them by ingesting it. Most humans and several homunculi are vulnerable to this technique.
That includes Scar, too, who can fend off the likes of Stain for a time, but not indefinitely. Stain is even quicker and more nimble than Scar, and he will most certainly find a chance to cut his larger opponent and activate that quirk of his. The mighty Scar goes down at last.
1 Can't Defeat: Alphonse Elric
Alphonse is in a similar position as Pride: he has no blood to start with. Instead, he is an artificial body, a human soul bound to a suit of armor. He doesn't like it, but in combat, he has the edge since he cannot get tired or bleed.
His alchemy and superhuman endurance will serve him well against Stain, and he's definitely immune to Stain's quirk. Most likely, Stain would realize this and simply leave. He's not going to bother trying against these odds.