some of the smaller cichlids can be just as aggressive, but most are colorful as opposed to 'bada$$' lookin. when i think of a mean lookin fish i'd have to go w/ pihrana or red-bellied pacu, the later of which really isn't that aggressive, just looks that way. but for both we're talkin 200 gallon tanks at a minimum.
check out the wolffish. i saw a baby one at a petstore onetime and thought he was the coolest thing. til i came home and found
this link . still, and amazing looking fish, even if they don't make the best aquarium fish.
orr, for a mere 125 gallons and a tight lid, you could get one of the best fish in aquaria today, Balantiocheilus melanopterus