cutthroat

[1]	murderer , pirate , killer , thug , hatchet man , gunman , assassin , (Slang) (US) gunsel , torpedo , hit man

adj.

[1]	merciless , fierce , bowelless , ruthless , unmerciful , unprincipled , relentless , pitiless , brutal , cold-blooded , cold-hearted
[2]	murderous , homicidal , lethal , deadly , barbaric , fierce , cruel , barbarous , savage , inhuman , brutal , brutish , violent , ferocious , bloodthirsty , sanguinary , bloody , feral , vicious , truculent