psychopath

A person who engages repeatedly in criminal and antisocial behavior without remorse or empathy for those victimized.

A morally irresponsible person.

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.

A person diagnosed with antisocial or dissocial personality disorder.

A person who has no moral conscience.

A person who perpetrates especially gruesome or bizarre violent acts.

someone with a sociopathic personality; a person with an antisocial personality disorder (`psychopath’ was once widely used but has now been superseded by `sociopath’)