1. Robert De Niro as Al Capone, The Untouchables (1987)
Playing the notorious Chicago crime lord Al Capone should be any actor's dream role. Not the biggest man in any room, Alphonse Gabriel Capone made up for his somewhat diminutive stature by always being the meanest, coldest, most ruthless gangster around (see: the 1927 Saint Valentine's Day Massacre). That was just amongst his illegally minded peers, though. To the public, he was a Robin Hood of sorts, using his dirty money to assist various charities.
It's a complicated acting assignment, no doubt, and in the 1987 Brian De Palma film The Untouchables, Robert De Niro killed the role in a monstrous, effectively sinister performance. Mixing charm with malice, De Niro's Capone sells icy dialogue like, about Treasury Department agent Eliot Ness (Kevin Costner), "I want you to get this fuck where he lives! I want his house burned to the ground! I wanna go there in the middle of the night and I wanna piss on his ashes!"
Capone's most memorable scene in The Untouchables involves a baseball bat, which he uses to bash a fellow mobster's head in, a moment inspired by a real-life 1929 incident where Capone bludgeoned three gangsters (John Scalise, Albert Anselmi, and Joseph "Hop Toad" Giunta) to death.
Fun method acting fact: In order to fully immerse himself in the role, De Niro always wore the same old-styled silk underwear that Capone wore. Hey, at least he was comfortable while going all Josh Hamilton on folks.