I have 2 bad boy ciclids that killed their tank mates when I wasn't around. Then the bigger almost killed the smaller. They have their own tanks. Otherwise I have community tanks.
My Senegals are in with a large angel that gets along with them but no one else. I am growing Yo-yo loaches and Synodontis Cats for that tank because the Senegals aren't aggressive or territorial. They just have, uh, culinary challenges.