Lou is a wonderful character, and his personal arc works in counter-point to the arc of the story. He is at his low point at the midpoint and at the end of act two, when he puts himself in greatest jeopardy by murdering the two drug dealers, he feels on top of the world. This is a wonderful and skillfully executed variation of the usual arc that finds the protagonist at his lowest point going into act three. Lou ends up doing something noble, letting Sally get away with the money to begin her new life, and the movie ends before we see what consequences may await him - he has his moment of glory, a big shot bad guy at last, and we leave him proud and grinning.