It Follows
The main character, Jay, is stuck with a parasitic "ghost" that slowly follows her around in an attempt to kill her. Only Jay can see it, and she has to give it to someone else by sleeping with them. The ghost takes on many different forms. Jay gave it to her friend, Paul, who gave it to a prostitute. The director opened it for interpretation, but most people agree that the woman that Paul gave the ghost to died, and now it's following Paul yet again.
Looper
Joseph Gordon-Levitt and Bruce Willis play young and older versions of the same hitman who is trying to take down a crime boss who ruins their lives in the future. They end up realizing that the crime boss wouldn't become the monster he was if his mother hadn't died, so to prevent that, Levitt's character kills himself which then kills Willis.