Besides Max Brass at the end of the campaign mode, Hedlok is the only being that counts a villain in the game.
Hedlok is a metal mask that goes on the top of a regular fighter and increases their ability to destroy everyone around them. One mode online has you fighting Hedlok with a team of three players.
Another gives you the chance to wear the helmet yourself and increase your speed. For the super attacks, it sends a devastating fireball which can't really be blocked either. When it comes your way, dodge! Well..if you can.
I don't mind Hedlok so much in the versus mode, but I always dreaded being assigned a match against the CPU. Unless your team is good, and you'll work together well, it will almost always end up in defeat.