8. Billy Costigan - The Departed
Why He's Awesome: Billy Costigan (Leonardo DiCaprio) is about to graduate from the Massachusetts State Police when he is approached by Captain Queenan (Sheen) and Staff Sergeant Dignam (Wahlberg) to infiltrate Frank Costello's (Jack Nicholson) outfit. This involves Costigan doing time in prison on an assault charge to make his cover more convincing, and against tremendous pressure, Costigan does a fantastic job easing into Costello's operation undetected.
How He Got Shafted: Queenan ends up murdered and Dignam is suspended, meaning that neither is really able to help Costigan when he gets in deep, despite being the only two who know of his identity. When he takes cop Colin Sullivan (Matt Damon) hostage - due to him being Costello's mole on the inside - he ends up being shot in the head by one of his fellow state troopers (Anthony Anderson) who refuses to listen to the truth. Though Costigan is awarded the Medal of Merit in the wake of his death, the film heavily implies that he is the father of psychologist Madolyn's (Vera Farmiga) baby, and so his son will grow up without his biological father.