I don’t know anything about the real-life boxer Jake La Motta, but I guess he was a scumbag who beat his wife and other people and trashed his career. For some bizarre reason, Hollywood decided to make a movie about him. The movie starts near the beginning of his career. He’s married and constantly argues with his wife. We never learn what happens to her. He meets the 17-year-old Vickie and takes off after her, eventually marrying her. He constantly thinks she’s cheating on him and beats her and everyone else. His manager is his brother Joey, whom Jake also beats up thinking he was messing around with Vickie. He fought Sugar Ray Robinson several times, winning some of them. He threw a fight and was barred from boxing for a while. He finally won the championship, but lost it again to Robinson. He quit boxing and bought a night club, but ended up in jail for solicting a 14-year-old girl. Vickie left him. At the end of his movie he’s doing a pathetic, vulgarity-laced routine in crumby nightclubs.

The movie was shot in black and white. De Niro gained 60 pounds to portray La Motta in later life. There’s not much to say. There’s nobody to root for and nothing to recommend it.
I watched it only because it was listed as one of the best 100 movies ever made. It convinced me to quit watching movies just because they were on that list.