3. Commodore Louis Kaestner
The primary antagonist of Seasons One and Two, the Commodore groomed Nucky Thompson to take over as Atlantic City boss. Trouble was, once that happened, the aging mobster didn't like the view from the cheap seats. By the end of the first season, the Commodore had enlisted both Eli and Jimmy to assist in his coup d'état, turning two of Nucky's closest confidants against him. Even a severe stroke the following season didn't incapacitate him for long – although it allowed Gillian to unleash her pent-up rage at him for raping her all those years ago (yep, the Commodore is Jimmy's dad – awkward!). In the penultimate episode of Season Two, Jimmy, in a drunken stupor, attempts to strangle Gillian, who made several callous remarks in the wake of his wife's death. The Commodore saves her by stabbing Jimmy in the shoulder with a spear, but his attempt to kill his own son is thwarted when the younger, stronger Jimmy finishes off his father instead.