One of the deepest action shonen anime shows out there is Fullmetal Alchemist: Brotherhood, which boasts tragic themes of hubris and mortal sin, forgiveness, the dual light and dark nature of humanity, genocide, and more. Still, there is plenty of time for action, and this series is all about alchemy and Homunculi.
There's a Homunculus for each deadly sin, and Greed is roughly in the middle of the pack. He has some martial arts skills and a great deal of courage, and he can harden his skin like diamond with his Ultimate Shield. He can also scratch with his sharp fingernails and regenerate any wounded flesh. With these assets, Greed can take on many fighters in other anime series... but not all of them.
10 Can Defeat: Eijiro Kirishima (My Hero Academia)
First, let's have Greed fight someone who's similar to him. Eijiro Kirishima is a student hero at U.A. in My Hero Academia, and his quirk allows him to harden his skin. That makes him an ideal melee fighter and human shield.
He's met his match against Greed, however, who can match his hard skin and outlast him thanks to superior strength and his capacity to regenerate any wounds he might suffer. Eijiro isn't ready for a villain like Greed just yet.
9 Can't Defeat: Baraggan Louisenbairn (Bleach)
This skeletal Arrancar is the 2nd Espada, Baraggan Louisenbairn. Few if any characters from Bleach or any anime can take him on, since he is the master of decay and time. Any matter or energy that gets close will rapidly age and rot away.
This death aura makes Baraggan difficult to even approach, let alone injure, and Greed has no angle here. He's got many souls in his Philosopher's Stone, but they'll all rot away (along with his flesh) once Baraggan gets in close and uses Respira (death breath). Then, Baraggan could cleave Greed's rotting body apart with his ax, Gran Caida.
8 Can Defeat: Josuke Higashikata (JoJo's Bizarre Adventure)
This is going to be a tough one, and it will cost Greed several regenerations from his Stone. But he can do it if he's persistent and takes Josuke by surprise. Greed can't destroy Josuke's stand (Crazy Diamond) since he doesn't have a stand of his own, but that won't stop him.
Instead, Greed just needs one chance to slip past Crazy Diamond (perhaps by exploiting the terrain) and get in close with Josuke himself. Crazy Diamond can fix and heal things, but the exception is Josuke's body, and Crazy Diamond will be helpless when Greed stabs his hand right into Josuke's chest.
7 Can't Defeat: Blackbeard (One Piece)
Blackbeard is a powerful pirate who wields the Dark-Dark Fruit, which allows him to create all-consuming black voids that can sink entire battlefields or ships at once. He became even more formidable when he stole the Tremor-Tremor Fruit from Whitebeard's dead body somehow.
Greed has no Devil Fruit powers, and his hard skin and martial arts skills won't mean much when Blackbeard creates a nether void with his Dark-Dark Fruit to swallow up Greed in total darkness. Not even the regenerative powers of the Philosopher's Stone will get Greed out of this one.
6 Can Defeat: Snek (One-Punch Man)
The hero known as Snek can give Greed a good fight, but he's not going to win this bout. He's one of the lowest A-Class heroes, meaning he can handle lesser villains just fine but needs reinforcements if a boss battle begins.
Greed is that boss battle, and Snek will have to give it his all to keep up. He's actually a little quicker and more nimble than Greed, but he has no special abilities or powers. Meanwhile, Greed has that hard skin and claws, plus regeneration. He can outlast Snek with ease.
5 Can't Defeat: Brandish (Fairy Tail)
Brandish is one of the Spriggan 12, the most powerful wizards of the Alvarez Empire. Even in that bunch, Brandish stands out with her immense magic and capacity to resize objects of any scale. She can even shrink down entire landmasses without trouble.
Greed is helpless before an ability like that. Brandish can shrink him to the size of a thumb, then toss him into a container and seal him away for good. Or she could turn herself into a giant and just step on him. In this case, size really does matter.
4 Can Defeat: Thorfinn (Vinland Saga)
Thorfinn is a Viking warrior, a boy born of the fearsome Thors, the "Troll of Jom." Thorfinn may not wield magic powers or a great hammer like Thor in the MCU, but he's a fearsome fighter all the same, and wields dual knives in combat.
That isn't going to cut it against Greed, since Thorfinn's knives can't cut Greed's skin while the Ultimate Shield is up. Thorfinn has superior maneuverability but Greed is too tough, and he'll land a serious blow on Thorfinn sooner or later in their duel.
3 Can't Defeat: Itachi Uchiha (Naruto)
Blades and punches don't work so well against Greed's hard skin and regeneration, but what about the advanced ninjutsu of Itachi Uchiha and his Mangekyo Sharingan? Greed is totally unprepared for an opponent like this.
Itachi's fireballs and shuriken won't make much headway, but his advanced genjutsu certainly will, and his Mangekyo powers can envelop Greed in all-consuming black flames or shatter his mind with torturous illusions. Greed's skin is tough, but he won't be ready to shield his eyes.
2 Can Defeat: Tanjiro Kamado (Demon Slayer)
In his own anime world, Tanjiro is a formidable fighter since he is tenacious, strong-willed, and rather talented with the demon-slaying Nichirin Blade. He has an affinity for water, and his desire to protect Nezuko has seen him through some serious fights.
But that Nichirin Blade has more limited power against Greed, who is certainly not a demon. Tanjiro can deal some damage in this duel, but Greed can survive the worst of it. Plus, he can slash Tanjiro's chest wide open with those steely fingernails of his.
1 Can't Defeat: Midnight (My Hero Academia)
My Hero Academia is packed with cool characters with fantastic abilities, so here's another character from that universe: Midnight. She has no means of piercing Greed's skin, but thanks to her quirk, Somnambulist, that's not necessary at all.
Instead, she can use her Somnambulist to release vapors from her skin. These vapors can put anyone to sleep once they inhale those fumes, especially men. Greed will conk right out, and Midnight can just walk away in victory. She doesn't even have to get her hands dirty.