Are you really looking for aggression or are you looking for personality? Something that's mean to other fish, or wants to get through the glass to you?
I'm looking for a fish with attitude and I'm thinking of setting up a green terror tank but I am still looking around. I was wondering if anyone has a different fish that is more prone to be aggressive but can still stay happy in a 75g or a 55 breeder.
Haplochromis sp. "#44" thickskin can be a pretty aggressive fish, they also are very pretty when all colored up. They are one of the more common vics, maybe a species tank with 1 male and 4-5 females