MUGEN's not really known for it's character balance, as most few characters usually end up being broken in a few ways, and only characters from existing fighting games that try to be source accurate aren't shattered like this.
So, what characters have you found that have overpowered attributes/moves sets? (Did you nerf them?)
My examples are... A PSX-Styled Omega Zero that could kill you in one hit using Rekkoha, or three hits with the O-Saber.
And MVC-Styled Hyper Sonic/Super Sonic that could kill you in one hit of any move.