i once had a jaguar cichlid that was absolutely nuts. it fought constantly with a oscar that was twice its size and ended up dying when it bit the head off an eal tail catfish and choked on it!!!

^ In that case I'd probably say piranhas. I think they're the only fish out of those mentioned whose teeth are designed to cut rather than hold. For just aggression though I'd say that aimara that SA has for sale...that thing is a beast.