Extremely evil or cruel; expressive of cruelty or befitting hell:
— A fiendish despot.

synonyms: demonic, diabolic, diabolical, hellish, infernal, satanic, unholy.

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 980: demonic, demonical, impish, demoniacal; fiendish, fiend-like; supernatural, weird, uncanny, unearthly, spectral; ghostly, ghost-like; elfin, elvin^†, elfish, elflike^†; haunted; pokerish [U.S.].    possessed, possessed by a devil, possessed by a demon.    ... show more

Roget 945: vicious; sinful; sinning etc. v.; wicked, iniquitous, immoral, unrighteous, wrong, criminal; naughty, incorrect; unduteous^†, undutiful.    unprincipled, lawless, disorderly, contra bonos mores [Lat.], indecorous, unseemly, improper; dissolute, profligate, scampish; unworthy; worthless; desertless^†; disgraceful, recreant; reprehensible, blameworthy, uncommendable; discreditable, disreputable; Sadistic.    base, sinister, scurvy, foul, gross, vile, black, grave, facinorous^†, felonious, nefarious, shameful, scandalous, infamous, villainous, of a deep dye, heinous; flagrant, flagitious; atrocious, incarnate, accursed.    Mephistophelian, satanic, diabolic, hellish, infernal, stygian, fiendlike^†, hell-born, demoniacal, devilish, fiendish.    miscreated^†, misbegotten; demoralized, corrupt, depraved.    evil-minded, evil-disposed; ill-conditioned; malevolent etc. 907; heartless, graceless, shameless, virtueless; abandoned, lost to virtue; unconscionable; sunk in iniquity, lost in iniquity, steeped in iniquity.    incorrigible, irreclaimable, obdurate, reprobate, past praying for; culpable, reprehensible etc. (guilty) 947.    unjustifiable; indefensible, inexcusable; inexpiable, unpardonable, irremissible^†.    weak, frail, lax, infirm, imperfect; indiscrete; demoralizing, degrading.    ... show more

Polish: demoniczny, szatański, sataniczny