Donnie Brasco (1997)

Johnny Depp goes undercover and befriends Mob guy Al Pacino. They become close. In the end, Al Pacino feels betrayed and Johnny Depp feels guilty, but Al Pacino's worse off because I think they shoot him (on a pier?). Basically Goodfellas meets Reservoir Dogs, maybe. Charlize Theron might be in this.

Not gonna last.