noun (n)

• a cruel wicked and inhuman person(noun.person)

  Synonym:
  demon, devil, monster, ogre
  

  source: wordnet30
• an evil supernatural being(noun.person)

  Synonym:
  daemon, daimon, demon, devil
  

  source: wordnet30
• a person motivated by irrational enthusiasm (as for a cause)(noun.person)

  Synonym:
  fanatic
  

  source: wordnet30
• An implacable or malicious foe; one who is diabolically wicked or cruel; an infernal being; -- applied specifically to the devil or a demon.(noun)

  source: webster1913