I have watched this show from beginning to end three times. I think it might be the best TV show in history. However, I disagree with the review above which says you can't say the protagonist, Vic Mackey, is a good or bad cop. In the first episode he murders one of his team members. He commits murder at least five times in the series. In the last episode he hangs his remaining partner out to dry (meaning that guy goes to prison for the rest of his life).
The brilliance of the show is in creating an atmosphere and story where we find ourselves confused time and time again by Vic's morality ... is he a good guy... is he a bad guy. This is the way that extreme narcissists survive in the world. The final episode, though, brings home a bleak message of the terrible costs, for everyone in his life, of Vic Mackey's way of being a cop. Everyone important to him is dead, in witness protection, or in prison.
He is a poisonous, dangerous, but very compelling and charming character. He gets things done, but causes more harm than good.