(n.) One who, or that which, exterminates.

Cain annihilator apache arsonist assassin assassinator biblioclast bloodletter bloodshedder bomber bravo burker burner butcher button man cannibal cutthroat demolisher desperado destroyer dynamitard dynamiter eradicator executioner garroter gorilla gun gunman gunsel hatchet man head-hunter hit man homicidal maniac homicide hun iconoclast idol breaker idoloclast killer man-eater man-killer manslayer massacrer matador murderer nihilist pesticide poison poisoner ruiner slaughterer slayer strangler syndicalist terrorist thug torpedo trigger man vandal wrecker