Martin Scorsese is legitimately one of the most talented directors of our time. Anyone interested in filmmaking should study him, and again here he is with an incredible crime /mob story. It is long (3.5 hours) but just incredible as a story. Top named actors, Al Pachino is one of my favorites.
That said, I have a problem with it, namely that it is based on a real life hitman that actually killed people, and the story is significant because it is based on a book that explains what might have happened to Jimmy Hoffa. The morals of the main character are so gut wrenching it will give you nightmares and the fact that this is about an actual person that did these things, it felt like the film was glorifying him. Im not a huge fan of movies that glorify criminals, its a reward / notoriety for their evil actions, seems culturally inappropriate.
Incredible movie, but bad juju. I probably would have preferred to not watch it.