Without mercy or pity:
— An act of ruthless ferocity.

synonyms: pitiless, remorseless, unpitying.

Roget 907: malevolent, unbenevolent; unbenign; ill-disposed, ill-intentioned, ill-natured, ill-conditioned, ill-contrived; evil-minded, evil-disposed; black-browed^†.    malicious; malign, malignant; rancorous; despiteful, spiteful; mordacious, caustic, bitter, envenomed, acrimonious, virulent; unamiable, uncharitable; maleficent, venomous, grinding, galling.    harsh, disobliging; unkind, unfriendly, ungracious; inofficious^†; invidious; uncandid; churlish etc. (discourteous) 895; surly, sullen etc. 901.1. cold, cold-blooded, cold-hearted; black-hearted, hard-hearted, flint-hearted, marble-hearted, stony-hearted; hard of heart, unnatural; ruthless etc. (unmerciful) 914.1; relentless etc. (revengeful) 919.    cruel; brutal, brutish; savage, savage as a bear, savage as a tiger; ferine^†, ferocious; inhuman; barbarous, barbaric, semibarbaric, fell, untamed, tameless, truculent, incendiary; bloodthirsty etc. (murderous) 361; atrocious; bloodyminded^†.    fiendish, fiendlike^†; demoniacal; diabolic, diabolical; devilish, infernal, hellish, Satanic; Tartaran.    ... show more

Roget 919: revengeful, vengeful; vindictive, rancorous; pitiless etc. 914.1; ruthless, rigorous, avenging.    unforgiving, unrelenting; inexorable, stony-hearted, implacable; relentless, remorseless.    aeternum servans sub pectore vulnus [Lat.]; rankling; immitigable.    ... show more

Roget 914a: pitiless, merciless, ruthless, bowelless; unpitying, unmerciful, inclement; grim-faced, grim-visaged; incompassionate^†, uncompassionate; inexorable; harsh etc. 739; unrelenting etc. 919.    ... show more

Polish: bezwzględny