TITAN triggers are crazy aggressive. Thats what I would say. Morays are agressive also, but in a more " I'm always hungry I want to eat you way". The Titan just kills everything, for no apparent reason.
A Blacktip Reef Shark is one of the last Sharks I would be afraid of. They have the speed and intelligence to be a threat, however they tend to have a more passive nature.
In my experience, golden travellies AKA pilot fish are the most aggressive of all saltwater fish. They aren't afraid of anything. They will even challenge sharks for their food.
As for bull sharks, my queensland grouper dominates my bull shark so bull sharks are really not that fierce.
i would have to say that the most meanist nastist fish i ahve come across would be....
a rock gunnel
jk but really i heard that dragon morays were pretty mean
dunno for sure though
Undulated triggers are consistently nasty across the board. With the exception of Titans, which I have no experience with, other triggers vary fish to fish. My clown trigger was the most laid back fish I've ever owned. Very surprising for a trigger.