ruthless

from WordNet (r) 3.0 (2006)

ruthless
    adj 1: without mercy or pity; "an act of ruthless ferocity"; "a
           monster of remorseless cruelty" [syn: {pitiless},
           {remorseless}, {ruthless}, {unpitying}]

from The Collaborative International Dictionary of English v.0.48

Ruthless \Ruth"less\, a.
   Having no ruth; cruel; pitiless.
   [1913 Webster]

         Their rage the hostile bands restrain,
         All but the ruthless monarch of the main. --Pope.
   [1913 Webster] -- {Ruth"less*ly}, adv. -- {Ruth"less*ness},
   n.
   [1913 Webster]

from Moby Thesaurus II by Grady Ward, 1.0

90 Moby Thesaurus words for "ruthless":
      Draconian, Tartarean, animal, anthropophagous, atrocious, barbaric,
      barbarous, beastly, bestial, bloodthirsty, bloody, bloody-minded,
      bowelless, brutal, brutalized, brute, brutish, callous,
      cannibalistic, cruel, cruel-hearted, demoniac, demoniacal,
      devilish, diabolic, dog-eat-dog, fell, feral, ferine, ferocious,
      fiendish, fiendlike, fierce, flinty, hard, harsh, heartless,
      hellish, implacable, inclement, inexorable, infernal, inhuman,
      inhumane, kill-crazy, malign, malignant, mean, merciless, mortal,
      murderous, noncivilized, pitiless, relentless, remorseless,
      sadistic, sanguinary, sanguineous, satanic, savage, severe,
      sharkish, slavering, subhuman, tameless, tough, truculent,
      unappeasable, unchristian, uncivilized, uncompassionate,
      uncompassioned, unfeeling, unflinching, unforgiving, ungentle,
      unhuman, unmerciful, unpitiful, unpitying, unrelenting,
      unremorseful, unsympathetic, unsympathizing, untamed, unyielding,
      vicious, wild, without mercy, wolfish