Synonyms of fiendish

Adjective

1. demonic, diabolic, diabolical, fiendish, hellish, infernal, satanic, unholy, evil (vs. good)

usage: 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"

Definition and meaning of fiendish (Dictionary)