Ridley, Toad, Dixie Kong, Mewtwo, Impa, a Ganondorf with a unique moveset
Just to name a few
ridley it's too disproprtionated to be a fighter...it's the kind of crature that looks good only standing still or flying (and that's how it has been portrayed in most of the games)..animating such creature for a fighting game while looking convincing would be next to impossible..even changing some of this chara design like trimming his wings
toad doesn't really have much to offer since in all the games all he does is smile and stay still,apart from mario 2 usa
dixie kong would have probably ended up being a clone of diddy
mewtwo already "evolved" to lucario years ago
IMpa is another character that didn't really do much in the games where she appears..i can just see her as a clone of sheik maybe
I agree for ganondorf with his own moveset though,maybe even in his pig form