FIENDISH
demonic, diabolic, diabolical, fiendish, hellish, infernal, satanic, unholy
(adjective) 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”
Source: WordNet® 3.1
Etymology
Adjective
fiendish (comparative more fiendish, superlative most fiendish)
Sinister; evil; like a fiend.
Synonym: conniving
Anagrams
• finished
Source: Wiktionary
Fiend"ish, a.
Definition: Like a fiend; diabolically wicked or cruel; infernal;
malignant; devilish; hellish.
– Fiend"ish*ly, adv.
– Fiend"ish*ness, n.
Source: Webster’s Unabridged Dictionary 1913 Edition