is a specific kind of: criminal, crook, felon, malefactor, outlaw | killer, slayer.

is a broader term that covers: assassin, assassinator, bravo | butcher | cutthroat | fratricide | gun, gun for hire, gunman, gunslinger, hired gun, hit man, hitman, shooter, torpedo, triggerman | hatchet man, iceman | infanticide | mass murderer | murderess | parricide | ripper | serial killer, serial murderer ... show more.

instances of which are: Jack the Ripper.

derivation: do in, knock off, liquidate, neutralise, neutralize, waste | bump off, dispatch, hit, murder, off, polish off, remove, slay.