The Departed

The Departed (Martin Scorsese, 2006) is a crime film that shows both sides of the law. The "goods" and the "bads". I'd recommed its soundtrack. I am sure you have heard it before.

  

Billy Costigan (Leonardo DiCaprio) is a cop who is assigned to infiltrate the mob syndicate run by Frank Costello (Jack Nicholson). Colin Sullivan (Matt Damon) is a member of the forementioned mob infiltrated in the state police as an informer. This is a film about the opposites side of the same fight.

I think that the film itries to make the viewer identify himself with both of them. 

Personally, I identify myself with Billy Costigan. I do not prefer him just because Leonardo DiCaprio, but also because I can understand his reasons, why he does what he does. This does not happens with Colin Sullivan.

Madolin (Vera Farmiga) knows Colin and Billy. Even more, she feels attracted by both of them. This is a film about both sides of an only conflict, but it also shows how similar both sides may be.

Frank Costello gives a grotesque and extravagant vision to the film.