Synonyms of fiendish in English:

fiendish


See definition of fiendish

adjective

1‘a fiendish torturer’

SYNONYMS
wicked, cruel, vicious, evil, nefarious, unspeakable
brutal, brutish, savage, barbaric, barbarous, beastly, inhuman, murderous, bloodthirsty, ferocious
ruthless, heartless, pitiless, merciless, black-hearted, unfeeling
malevolent, malicious, villainous, malignant, devilish, diabolical, hellish, demonic, satanic, Mephistophelian, ungodly
odious, base
archaic, humorous dastardly

2‘a fiendish plot’

SYNONYMS
cunning, clever, ingenious, artful, crafty, canny, wily, guileful, devious, scheming, shrewd, astute, sharp, sharp-witted, imaginative
informal foxy, savvy, sneaky, cute
Scottish, Northern English informal pawky
South African informal slim
rare vulpine, carny

3‘a fiendish puzzle’

SYNONYMS
difficult, complex, complicated, intricate, involved, knotty, thorny, ticklish, abstruse, impenetrable, unfathomable
challenging, puzzling, baffling, perplexing, bemusing
frustrating