my tank has no boss. lol the O'opu is in a constant rumble with the JD but the JD wins slightly more often, still pretty even though. the oscar scolds the JD but rarely. the plecos have their own fights, the arowana gets caught between the oscar eating or the JD running from the O'opu and gets scared.
My Emperor cichlid is the boss of the tank,if any other fish get into any squabbles the emp chases them around for a while.He even splashes the water surface sometimes when I put pellets in to keep other fish from eating and then after a while he will let them eat.
In my 55gal African tank, one of my Johannii is definitely the ruler. He bullies the other johanni almost constantly, I might remove that one from the tank..everyone else mostly steers clear of him.