Synonyms and related words :
bowelless, cruel, flinty, hard, harsh, heartless, inclement, inexorable, merciless, pitiless, relentless, remorseless, ruthless, uncompassionate, uncompassioned, unfeeling, unforgiving, unmerciful, unpitiful, unpitying, unremorseful, unsympathetic, unsympathizing, unyielding, without mercy