Beasts! Just by looking at the cast of the departed you know you are about to see something very very good. Also, breaking the rules! No spoilers will appear in the next lines! Watch the departed! Especially if you like complex plots, "strategic" movements, gangs, police investigations and all these goodies. 2 and a half hours of jaw dropping excitement just from pure strategic movements.
Our main protagonist, antagonist and villain are the 2 cops and the head of a gang respectively. After about watching half the movie, you might think that you are going to see the third act and close the film. You are going to experience this several times. Without any big scenes and explosions, the departed is all about keeping you interested and excited with the plot, the lines and the skills of the actors who inject tension in you.
A long movie, not for the faint of heart. The score given talks by itself. Just enjoy the movie.
"Dignam: I'm the guy who does his job. You must be the other guy."
"Queenan: Do you want to be a cop or only look like a cop?"
"Queenan: You're a worker. You rise fast. Dignam: Like a 12-year-old's d!*k."