Synonyms and related words :
bowelless, callous, coldhearted, cruel, disagreeable, dog-eat-dog, flinty, hard, hard-boiled, hardhearted, harsh, heartless, ill, inclement, inexorable, inhospitable, merciless, obdurate, pitiless, relentless, remorseless, ruthless, unaffectionate, unamiable, unbenign, unbenignant, uncompassioned, uncordial, unemotional, unfeeling, unforgiving, ungenial, ungracious, unkind, unkindly, unloving, unmerciful, unpitiful, unpitying, unremorseful, unsympathetic, unsympathizing, unyielding, without mercy