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