I'd say the Genovese and Benny Squint, but the Chicago guys deserve an honorable mention. The fact that Ricca pretty much told Nitti to take the charge for the movie union thing, and got all the other guys to side with him, says something. It implies that Nitti never had the real power anyway and it was Ricca running things all along. There's also that cop and a couple of others who claim that Ricca was still the real boss and that nothing got done without him knowing about it, even when Accardo was boss and even parts of Giancana's reign.