My 11" Rose Queen is my most aggressive. He chews the heck out of me during tank maintenance (have to wear Aquagloves) and kills anything put in his tank. He won't even eat other fish, I put in a couple goldfish I didn't have room for anymore and he just immediately killed them, but didn't eat them.
My FM so far. She is the most aggressive 3" fish I have ever seen. I would be suprised if she can take a 8 inch jag on and win. I love her aggressiveness but makes tankmates hard to find for her.