With a few exceptions, I don't consider most cichlids aggressive in the proper sized tanks, but in too small tank, any and all will get aggressive.
I've kept over 100 different species over the years, from dwarfs to P-bass and dovii.
I consider oscars pussy cats in the right size tanks, and red devils only mildly aggressive, as long as there was sufficient territorial room and any of the so called "terrors" (green or red) only moderately aggressive in the proper size tank.'
Of the medium to large size cichlids I believe Heterotilapia buttikoferi is wackiest no matter what size tank under 300 gallons.
Of the small cichlids Neetroplus nematopus can be quite aggressive, against other cichlids 4 or 5 times its size.
And Coptodon bythobates are up there when spawning.
I had a pair of bythobates that would hunt down another fish in the tank, and bring its carcass to its fry for food, and then do it again when the fry polished that carcass off. When fry were raised, it became another pussycat