Honestly, i barely remember most of his moveset, it has been a long time since i played that game, so i'll "explain" it with a picture.
Elaborating:
Zero: Beeg normals. Shadow Clone Jutsu. Infinite to death.
Phoenix: Get 5 bars. Die but not really. Become the most broken character in the game. Vomit projectiles and traps everywhere. Do a billion damage with your combos. I think she can also break combos in certain circumstances because all of her buttons create projectiles.
Morrigan: Mirror Clone Jutsu. SOUL FIST! SOUL FIST! SOUL FIST! SOUL FIST! SOUL FIST! SOUL FIST!
Vergil: Beeg normals. Summons swords that create a passive hitbox all around him. X-Factor makes him do a billion damage. K.O.ing the entire team off of X-Factor is very common.
Doctor Doom: Broken assist that constantly harrasses opponents by dropping missiles on their head. Dive Kick Infinite. Can spend all of his time in the sky shooting projectiles at you.
Magneto: I don't actually know the specifics of this one, but I'd wager it has to do with his movement, as his 8-way dash makes him a speedy boy.
The cancer teir is also kinda funny, and while I don't know the specifics about half of them, given what I know about the other half I think it's the "has strange mechanical interactions that make them utter dogwater" teir. Phoenix Wright is purposely garbo until he gets his evidence, and has to play rediculously defensive as a non-zoner in order to get his install and be actually good. Hsein-Ko can't wavedash because of how her air dash works, and her air dash is really,
really slow so she just doesn't have mobility full stop, and on top of this a decent amount of her stuff is random and unreliable, to include her damage super. Nemisis is big and slow, and his hitboxes are super jank to the point where his level 3 just doesn't hit even when it should.