side-stabber
someone who has stabbed in the back like a coward and in the front like a courageous asshole so many times that its hard to tell which one they are
'Cedric is such an ambivalent curio. A pure blooded side-stabber if there ever was one. He secretly screwed me out of $100 last week, then he told his boyfriend that he was having an affair with his mother, then he actually butchered his girlfriend with a dirk from all angles'