I have owned a bunch of cichlids. With 30 years of experience the top 5 most aggressive would be.
1.) Buttikoferi Tilapia. These guys are nothing but evil. Do not let his mouth fool you, they crush & rip the lips off of all their enemies. The pressure in their bite is ridiculous. Giving me 9 stitches on my hand and eating the stomach's off other fish. These guys should never be trusted, they are born mean. Remember these monsters get to 20''(20 inches), enough to take on any dovii at that size.
2.) Dovii Cichlid. The wolf cichlid, these guys are huge beasts. They have very large teeth, large mouths, and a muscular body. Not so aggressive when small, but once they reach 6 or more inches they dominate almost all their tank mates. Don't ever under estimate these guys, they are capable of doing a lot of damage to YOU and other FISH.
3.) Umbee Cichlid. Another big cichlid like the Dovii. They are easily the largest Central American cichlid you could own in the hobby. These guys are actually quite cute when young, but when they get older the tides turn. They get a large mouth, teeth, strength, and become ferocious. They are called the "Blue Freckled Monster" for a reason.
4.) Nandopsis Beani. A very rare guapote. These guys freak out when kept with other fish. At a foot long they can take a 200 gallon to themselves. These guys are hyper aggressive, but they are
susceptible to bloat. Due to this, they usually get severely sick if they fight or have poor water conditions. There is no other cichlid at 12 inches like the beani and will take on a cichlid like the umbee that is 26 inches. No cichlid has the confidence like the beani.
5.) Red Devil Cichlid. The name says it all. These guys are nothing but killers. They are very common and are known to kill all the cichlids Above
. Red Devil's are great cichlids though, full of personality. Remember these guys need close attention when mixed with other tank mates(fish). One tough Demon.
Thats my list...