This is one of the best written films of all time, in my opinion. And no, it's not my favourite film. I don't rewatch it; it isn't one of those movies. It's meant to be as dark and disturbing as it is. But, is it incredibly written, and executed? Absolutely.
Johnny, played by David Thewlis, is one hell of a main character. He is complex, and he is complicated. Some may look at him and see a monster for being a rapist, which he is, and I am in no way excusing it; rape disgusts me as it should disgust and horrify everyone on this planet; but we, the audience, realises as the movie goes on, that Johnny is more than his heinous actions.
He is lost. He doesn't have a home, doesn't feel safe, doesn't feel understood. He has so many thoughts, so many things he wants to say, so many things he feels.
The movie does an incredible job of distracting the audience from Johnny's actions, and is so well done.