It really depends on how you define "aggressive looking".
If you mean - something that looks like a requiem Shark or a Hammerhead - then the short Answer would be no.
But if you define "aggressive looking" - as cool looking, voracious feeder, that doesn't need to constantly swim - then it certainly possible to keep some species for at least a little while in a 500-600 gallon tank.
Some cool looking species that tend to be voracious feeders include the following.
-"Dwarf" Wobbegongs - these are species of Wobbegongs that have a maximum size of less than 39 inches(99 cm) in length. Such species include the Japanese Wobbegong, the Northern (Ward's) Wobbegong, and the Cobbler Wobbegong.
- Horn Sharks(Bullhead Sharks) - while most available species will eventually get to be nearly 4 ft (120 cm) or more in total length. They also tend to be fairly slow growers, and may take several years to outgrow a 500 gallon tank. They also have a cool prehistoric shark look to them.
- Coral Catsharks - While they resemble "eel-like" sharks in their general appearance. they are know to swim in a very requiem shark style, and often come out to hunt as the lights go out.