Well, the time i took my 10" Amphillophus Sagittae out of his 65G and popped him in my 130G with other cichlids to see how he would do it wasn't good. My 9" Braziliensis and my 7" Jack Dempsey who were in mid tussle themselves stopped what they were doing, turned a funny color and headed for the corners of the tank. The JD, a beautiful blue spangled fish literally went white. That was just the mere sight of this beast of a fish swimming amongst them. The other fish all gave him a wide berth too, a couple of hours later he was pushing and chasing most of them around until i took him back out and put him back in his 65G. After a while he grew to a point where he was too big for that tank so i traded him.
I've had other experiences with Red Devil complex that haven't appeared to be causing too much trouble but then upon switching the lights on in the morning i've noticed several other fish have scales missing.
In my experience these guys are about the most violent and destructive i've come across and there aren't too many i haven't tried. They're quite possibly my favourite, but i've given up trying to keep them.