psychopath
A person with a personality disorder characterized by persistent antisocial behavior, impaired empathy and remorse, and bold, disinhibited, and egotistical traits. Used in both clinical and colloquial contexts.
He was diagnosed as possibly being a psychopath.
The villain in that movie is a typical psychopath.
The criminal was diagnosed by a doctor as a psychopath.
His behavior shows some psychopathic tendencies.