Below are possible answers for the crossword clue Fiendish.
7 letter answer(s) to fiendish
DEMONIC
extremely evil or cruel; expressive of cruelty or befitting hell; "something demonic in him--something that could be cruel"; "fires lit up a diabolic scene"; "diabolical sorcerers under the influence of devils"; "a fiendish despot"; "hellish torture"; "infernal instruments of war"; "satanic cruelty"; "unholy grimaces"
10 letter answer(s) to fiendish
DIABOLICAL
extremely evil or cruel; expressive of cruelty or befitting hell; "something demonic in him--something that could be cruel"; "fires lit up a diabolic scene"; "diabolical sorcerers under the influence of devils"; "a fiendish despot"; "hellish torture"; "infernal instruments of war"; "satanic cruelty"; "unholy grimaces"
showing the cunning or ingenuity or wickedness typical of a devil; "devilish schemes"; "the cold calculation and diabolic art of some statesmen"; "the diabolical expression on his face"; "a mephistophelian glint in his eye"
4 letter answer(s) to fiendish
EVIL
having or exerting a malignant influence; "malevolent stars"; "a malefic force"
having the nature of vice
morally bad or wrong; "evil purposes"; "an evil influence"; "evil deeds"
morally objectionable behavior
that which causes harm or destruction or misfortune; "the evil that men do lives after them; the good is oft interred with their bones"- Shakespeare
the quality of being morally wrong in principle or practice; "attempts to explain the origin of evil in the world"
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