I don't know what to say about this movie. So I'll let someone from IMDB do the talking. I like what he has to say anyway.
deeply unpleasant movie with a star performance
'Bad Lieutenant' is not an easy film to watch. The lead character on the surface has no redeeming virtues - he's corrupt, he's sexually and morally deviant, he is really and truly on the slide. A nun's rape is supposed to awaken his conscience in some way and affect him so deeply that he almost gets to be a decent citizen, but for the bleak and empty ending.
All this would be so much hogwash if it wasn't for the stunning lead performance of Harvey Keitel, certainly taking his acting talent right to the edge to give us a nothing-held-back portrait of his character. There are several scenes of great power (and one or two which are deeply repellent); certainly this isn't a film you can easily forget when you've seen it.