green sunfish are far more aggresive than pumpkinseeds, so far my green has killed one red devil and beat up my jag and dempsey. theres no real way of knowing which cichlid is the toughest. yeah we know which ones are the baddest but the only real way to know for sure it to do a best out of ten test, get ten of each fish and see which ones win the most fights. i know the thought of it is insane and stupid but thats the only thing that i can come up with. every single fish has its own peronality type, some are assholes and others are passive. ive had sunfish get beat up and other ones that wont tolerate other fish at all. RDs have a rep for beating up texas cichlids but ive seen a red devil with its bottom jaw half torn off by a tex of equal size. it all depends on the fish