[adj] having or showing no mercy; "the merciless enemy"; "a merciless critic"; "gave him a merciless beating"
bowelless, cutthroat, fierce, mortal(a), pitiless, remorseless, ruthless, tigerish, unmerciful, unpitying
merciful
atrocious, barbarian, barbaric, barbarous, bestial, bloody, bowelless, brutal, brutish, callous, cold, crude, cruel, cutthroat, dog-eat-dog, feral, ferine, ferocious, fierce, hard, harsh, heartless, illiberal, implacable, inclement, inconsiderate, indiffe