psychopath
Clinical or formal term for a person with psychopathy. In everyday conversation, サイコパス is more common.
Psychopaths are said to have a marked lack of empathy for others.
More common in everyday speech and media. 精神病質者 is a formal, clinical term.
Compound of 精神 (mind), 病質 (pathological disposition), and 者 (person). A direct translation of the Western clinical concept.