Having the strongest member of the team be a pacifist was an interesting dynamic for a while. Probably the story potential of that fizzled out once Rogue joined, as she was also ungodly strong and could fly and do other things in addition (not much tension in Piotr having a page of thought bubbles about whether he should fight or not when Rogue would just zip in from off frame and finish the fight without him). Don't think making him a psycho would do anything but undermine him as a character.