ruthless, merciless, relentless, pitiless, murderous, brutal, savage, coldhearted, diabolical, implacable, unrelenting, brutish, maniacal, motiveless, unmerciful, ferocious, callous, unremitting, inexorable, ceaseless, vengeful, sociopathic, unregenerate, somnambulistic, demented, bloodthirsty, machinelike, cunning, fiendish, monomaniacal, sadistic, heartless, depraved, amoral, conscienceless, rapacious, nihilistic, ghastly, methodical, unremorseful, manic, machiavellian, obsessive, monstrous, cruel, vicious, psychopathic, unrepentant, emotionless, unfeeling, obsessional, imperious, fearsome, unforgiving, mindless, unblinking, steely, hardbitten, avaricious, stoical, grotesque, ravening, saturnine, monkish, mulish, chilling, peerless, wretched, ineluctable, sanguinary, purgatorial, vile, insensate, crazed, nerveless, joyless, impenitent, insane, cowardly, megalomaniac, lumpen, barbarous, beastly, perfidious, bestial, unyielding, impassive, palsied, thuggish, dostoyevskian, loathsome, paranoiac, unthinking, verminous, perverse, inhuman, dostoevskian, insidious, tormented, deathly, pertinacious, psychotic, unsparing, unstoppable, revengeful, unpitying, vindictive, resistless