Currently, my Purple tang is top of the food chain in my tank. Not overly aggressive, but doesn't put up with any nonsense. It has gone after my hand when I was cleaning and moving rock, I felt the tail swatting at me.
In my old 300 gallon, my Achille's that I had for almost 3 years, became a complete monster. I wound up selling it due to its extreme aggression toward all the large Angels in the tank.