8. Joe Masseria
Behind Charlie "Lucky" Luciano, Gyp Rosetti and now Dr. Valentin Narcisse, there was New York mob king Joe Masseria, standing in the shadows and working the puppet strings of all the city's lower-level gangsters. He epitomizes the old-world ways of conducting business (in his case, speaking primarily in Italian, and expressing doubt over Luciano's partnership with the Jewish Meyer Lansky), but it makes him no less powerful along the Eastern seaboard. He was the brains behind Owen Sleater's jaw-dropping Turkish-bath murder in Season Three, sending the Irishman back to Nucky (and his pregnant mistress, Margaret) stuffed in a wooden crate. By the end of Season Four, Masseria had joined forces with Narcisse to control the burgeoning heroin trade, making him all but untouchable.