slayer

from WordNet (r) 3.0 (2006)

slayer
    n 1: someone who causes the death of a person or animal [syn:
         {killer}, {slayer}]

from The Collaborative International Dictionary of English v.0.48

Slayer \Slay"er\, n.
   One who slays; a killer; a murderer; a destroyer of life.
   [1913 Webster]

from Moby Thesaurus II by Grady Ward, 1.0

41 Moby Thesaurus words for "slayer":
      Cain, apache, assassin, assassinator, bloodletter, bloodshedder,
      bravo, burker, butcher, button man, cannibal, cutthroat, desperado,
      eradicator, executioner, exterminator, garroter, gorilla, gun,
      gunman, gunsel, hatchet man, head-hunter, hit man,
      homicidal maniac, homicide, killer, man-eater, man-killer,
      manslayer, massacrer, matador, murderer, pesticide, poison,
      poisoner, slaughterer, strangler, thug, torpedo, trigger man