unmerciful

from WordNet (r) 3.0 (2006)

unmerciful
    adj 1: having or showing no mercy; "the merciless enemy"; "a
           merciless critic"; "gave him a merciless beating" [syn:
           {merciless}, {unmerciful}] [ant: {merciful}]

from The Collaborative International Dictionary of English v.0.48

Unmerciful \Un*mer"ci*ful\, a.
   Not merciful; indisposed to mercy or grace; cruel; inhuman;
   merciless; unkind. -- {Un*mer"ci*ful*ly}, adv. --
   {Un*mer"ci*ful*ness}, n.
   [1913 Webster]

from Moby Thesaurus II by Grady Ward, 1.0

48 Moby Thesaurus words for "unmerciful":
      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