Synonyms of merciless

1 Syllable

hard, cruel, harsh, grim

2 Syllables

crueler, stony, ruthless, cruelest, brutal, wanton, fierce, grimmer, lowbrow, stonier, wreakful, feller, cutthroat, grimmest, callous, heartless, mortal

3 Syllables

ferocious, inhuman, barbarians, unyielding, ruffianly, pitiless, death-dealing, dog-eat-dog, uncordial, hardhearted, barbarian, unflinching, tigerish, unsparing, severe, unpitying, onerous, coldblooded, ferine, barbarous, relentless, cold-blooded, gratuitous, hard-shelled, unfeeling

4 Syllables

ironhearted, unforgiving, remorseless, stony-hearted, implacable, unrelenting, unamiable, uncalled-for, unmerciful, compassionless, iron-fisted, singleminded, overtaxing, stonyhearted, vindictive, unrepenting, inhumane

5 Syllables

inexorable, unappeasable, unsympathetic, unsympathizing, uncharitable