Ruthless

a.

1.

Having no ruth; cruel; pitiless. Their rage the hostile bands restrain, All but the ruthless monarch of the main. - Pope.

Adj.

1.

ruthless - without mercy or pity; "an act of ruthless ferocity"; "a monster of remorseless cruelty" Synonyms: pitiless, remorseless, unpitying

Draconian, Tartarean, animal, anthropophagous, atrocious, barbaric, barbarous, beastly, bestial, bloodthirsty, bloody, bloody-minded, bowelless, brutalized, brute, brutish, callous, cannibalistic, cruel-hearted, demoniac, demoniacal, devilish, diabolic, dog-eat-dog, fell, feral, ferine, ferocious, fiendish, fiendlike, fierce, flinty, hard, harsh, hellish, implacable, inclement, inexorable, infernal, inhuman, inhumane, kill-crazy, malign, malignant, mean, merciless, mortal, murderous, noncivilized, pitiless, relentless, remorseless, sadistic, sanguinary, sanguineous, satanic, 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