psychopath

noun

1. 1.A person with a personality disorder indicated by a pattern of lying, cunning, manipulating, glibness, exploiting, heedlessness, arrogance, delusions of grandeur, sexual promiscuity, low self-control, disregard for morality, lack of acceptance of responsibility, callousness, and lack of empathy and remorse. Such an individual may be especially prone to violent and criminal offenses.
2. 2.A person with no moral conscience who perpetrates especially gruesome or bizarre violent acts.
3. 3.A person diagnosed with antisocial or dissocial personality disorder.
4. 4.A person diagnosed with any mental disorder.