For me it would be the black piranha I had when I was a teenager. This piranha was the most mean fish I have ever had. I actually took the piranha back to the pet store and that was that. Back then I did not know much about piranha and I did not know what I had. I wish I understood what I had and then I would not have sold him back to the pet store. Now I own another black piranha and many other piranha and I love them all.
Buttikoferi cichlid pound for pound..My friend owns one, it is about 16 inches 8 years old..this fish has killed dovii's,devil's,oscar's, and too many he can't even remember! lol