They are all aggressive if the tank is too small.
Aggression is a term used to often. Territorial behaviour is based on securing a territory. If the tank is big enough to provide the space required for a particular species to set up a territory, territorial behaviour will be diminished.
Aggressive behaviour only occurs when other fish can not leave the cichlid pairs territory.
Aggressive behaviour will be observed more by species that set up larger territory in nature. For example, Dovii set up a territory roughly the size of a small tennis court.If we are to house a dovii pair in a tank of 500 gallons they will still behave aggressively to other cichlids that enter that tank as their natural exclusion zone centered around a spawning site will be far greater than the tank can provide.
On the other end of the scale,a firemouth will make do with a few inches for a territory, therefore it's space requirements can be met in more modest tanks such as a 75 gallon.
Cichlids are not aggressive by nature,they just want to mate and bring up their young in their own space.
If i were to make love to my wife and some random stranger kept popping into our bedroom I would behave aggressively, that does not make me an aggressive person.
If cichlids are aggressive in your care, you are keeping them incorrectly.
If you want to witness aggression in your tank, then I can't help.
Aggressive cichlids= incorrect housing.