Ha! My Dempsey was a pansy too. That video doesn't make sense to me, unless that Dempsey is a female and it laid eggs (which the gill plate does have the indicative blue sheen of a female, but I'm no expert or even apprentice on sexing those fish).
That's nuts how mad that Dempsey is! But, like the boxer it's named after, the Dempsey fights a fair fight. Convicts, much akin to their respective nomenclature, fight with prison rules. I had convicts that wouldn't lip lock, but would instead just bite the sides and fins of fish twice the size of them, and then retreat somewhere that the bigger fish couldn't go. Convicts are just plain BRUTAL. I remember I had a 3" male convict bite the whiskers of a huge pictus catfish I had in my 125 gallon SA/CA community tank, and the catfish let out a bubbling yell. I think that was the last straw, and I gave the convict back to the place I bought it from.
The cichlid that started it all for me was the bolivian ram. I unknowingly bought a pair for my community tank, and I had since only kept livebearers and tetra. It was weird seeing fish with personality, and most of all, fish that would actually USE the decor that I blew money on for the tank. Fish before cichlids were such boring impersonable creatures to me. Tetra just sort of seize their way around an aquarium, with quick jutted motions, and I never knew if they were thriving or dying.