Cutthroat

Noun

 * 1) A murderer who slits the throats of his victims.
 * 2) An unscrupulous, ruthless or unethical person.

Adjective

 * 1) Involving the cutting of throats
 * 2) Of or relating to a card game where everyone plays for him or herself rather than playing with a partner.
 * He found that playing cutthroat Spades was much more difficult than playing with a partner.
 * 1) Ruthlessly competitive, dog-eat-dog
 * Law is a cutthroat business, you always have to look out to see who is trying to outdo you.

Thesaurus
Cain, apache, assassin, assassinator, barbaric, barbarous, bloodletter, bloodshedder, bloodthirsty, bloody, bloody-minded, bravo, brutal, brutish, bucko, bully, bullyboy, burker, butcher, button man, cannibal, cold-blooded, competing, competitive, cruel, deadly, desperado, devil, emulous, eradicator, exacting, excessive, executioner, exorbitant, exterminator, extortionate, extravagant, fancy, feral, ferocious, fierce, garroter, gorilla, gory, gouging, grossly overpriced, gun, gunman, gunsel, gunslinger, hatchet man, head-hunter, hell-raiser, hellcat, hit man, homicidal, homicidal maniac, homicide, immoderate, in competition, in rivalry, inflationary, inhuman, inordinate, killer, lethal, mad dog, man-eater, man-killer, manslayer, massacrer, matador, merciless, murderer, murderous, out of bounds, out of sight, outrageous, overpriced, pesticide, pirate, pitiless, poison, poisoner, preposterous, prohibitive, red-handed, relentless, rival, rivaling, rough, rowdy, ruffian, ruthless, sanguinary, savage, self-destructive, skyrocketing, slaughterer, slaughterous, slayer, spiraling, strangler, suicidal, thug, torpedo, trigger man, truculent, unconscionable, undue, unmerciful, unprincipled, unreasonable, unwarranted, usurious, vicious, violent, vying

Alternative forms

 * cut-throat