Raphael

Raphael was the Turtle best known for his sarcastic mouth and hair-trigger temper.  In the Mirage universe, he was also extremely violent; while most of his brothers in this incarnation would kill opponents if needed, Raphael didn't seem to have much remorse afterwards.  He was often found out on patrol with Casey Jones, or, in later issues, at the bar with his drinking buddy Cha Ocho.

In volume 4, Raphael was bitten by a vampire-like, and became supermutated.  He doubled in size and became very much a monster, going on a rampage, and not having any thoughts about what he was doing.  It was only through Splinter's meditative guidance that Raphael was able to gain some control over himself.