List of fiendish synonyms and fiendish related words.
Draconian, Mephistophelian, Tartarean, animal, anthropophagous, atrocious, bad, baleful, barbaric, barbarous, beastly, bestial, bloodthirsty, bloody, bloody-minded, brutal, brutalized, brute, brutish, cannibalistic, cruel, cruel-hearted, cursed, damnable, demoniac, demoniacal, demonic, demonish, demonlike, devil-like, devilish, diabolic, diabolical, evil, execrable, fell, feral, ferocious, fiendlike, fierce, ghoulish, heinous, hellborn, hellish, infernal, inhuman, inhumane, malefic, maleficent, malevolent, malicious, malign, malignant, monstrous, murderous, ogreish, outrageous, ruthless, sadistic, sanguinary, sanguineous, satanic, savage, serpentine, sharkish, sinister, slavering, subhuman, truculent, unchristian, uncivilized, ungodly, unhallowed, unhuman, vicious, wicked, wolfish