Sociopaths, not psychopaths. Psychopaths lack planning ability and often exhibit poor impulse control. They're often pretty easy to spot since their behavior is generally obvious.
Sociopaths, on the other hand, are very much worse. They are clever enough to "pass" and to create and pursue long term plans.
I have unfortunately worked with one guy that seemed to me to be pretty far along on that continuum of sociopathy. He was constantly backstabbing and manipulating and really fucked me over hard, all because he saw it as a way to get ahead. He lied, dissembled, and only in a truly transparent group setting was I able to call his actions out.
I went on Christmas vacation with everything "good" with my team and came back to my manager asking me why my module was "completely fubared," according to my colleague. So I sat down with my manager and my accuser and went through the code line-by-line to explain the function and reasoning behind the code, then showed it working in our codebase repo. My accuser, with nothing else to throw at me said that he "had been confused by the names of the classes."
He still managed to convince management that I didn't deserve a bonus and he did, despite his poor track record. THAT is the danger of these sorts of people, and a hard lesson learned that I _have_ to play politics enough that I am sure I am not being thrown under the bus rather than just focusing on being a creative and productive member of the team.
While my manager and the accuser were good buddies through most of the project, the accuser's true nature began to shine through and now he's moved across the country, presumably with new bridges to burn.