Tommy Pitera killed many, many people. Just as an example that should suggest he killed more than we know of - he was at a crew member's apartment one day, and the crew member's girlfriend was present as well. During the time hanging out, he assassinated the man's girlfriend, with no warning and absolutely no motive. He just did it. Just like that. Lepke Buchalter was really ridiculous. I believe Joe Valachi when he says Lepke and Gurrah Shapiro killed for their own gang, not for The Commission. Lucky Luciano was never violent enough to order really any of those murders.

Machine Gun Jack McGurn might be up there, and later, Chuckie Nicoletti. Ignazio Saietta (basis of Don Fanucci) never had much of his own gang when he was independent, yet frequently committing 'maintenance murders' just to keep the town terrified. He's got to be way up there.