Most fighting games use different moves / move abilities to give their characters personality.

Using Chun-Li and E.Honda from Street Fighter two for example:

Both had the ''fists of doom'' type move. Chun-Li used her feet, E.Honda used his hands.

Chun-Li could jump further, and bounce off walls.

etc...

This is probably the easiest way to give your characters personality.. A state machine customized for each character determines their fighting style.

Will