Raging Bull (1980)
Sorry, this movie sucks
At first rather annoying in its heavy emphasis on reenactments, this movie ultimately proves fascinating, simply because the complicated, highly dramatic tale it tells still almost defies belief.
This is one of the few movies I've ever seen where the whole audience broke into spontaneous, loud applause a third of the way in.
The best films of this genre always show a path and provide a takeaway for being a better person.