Synonyms and related words :
barbarous, bowelless, brutal, brutish, callous, calloused, cold, cold of heart, coldblooded, coldhearted, cruel, dog-eat-dog, flinthearted, flinty, hard, hard of heart, hardened, hardhearted, harsh, heartless, inclement, inexorable, insensitive, mean, merciless, obdurate, pitiless, relentless, remorseless, ruthless, savage, stonyhearted, uncompassionate, uncompassioned, unfeeling, unforgiving, unkind, unnatural, unpitiful, unpitying, unremorseful, unresponsive, unsparing, unsympathetic, unsympathizing, unyielding, vicious, without mercy