Once Upon a Time in America (1984)

Apparently you really need to have four hours of movie in order to really understand the story of  David "Noodles" Aaronson (Robert De Niro) over the course of his live.  
The movie tells the story of five decades in the lives of four gangsters from New York City -- childhood friends who are merciless criminals almost from the first, but who have a special bond of loyalty to each other.  Noodles has a couple of breaks with the gang.  The first is that he goes to jail for the sake of the gang after killing a rival gangster who is twice his age at the the time.  The second is an act that the viewer sees about mid-movie and that is the one that both haunts him and is mysterious.
The movie shifts between their growing up in a Lower East Side slum  in the 1920's, their antics in the 1930's running booze in Prohibition, and then their next criminal enterprises, and then 1968 when Noodles returns to the scene of the crime after decades in hiding to come to terms with his past.  There is a lot of story to digest here, and I am not sure that I really got the deeper meaning of it all, but it is an impressive De Niro movie I had missed up until now.