Fiendish

прилагательное злодейский, дьявольский, жестокий Синоним(ы): devilish, damnable

Большой англо-русский словарь

Fiendish

adjective 1. perversely diabolical Example: took a fiendish pleasure in hurting people 2. extremely cruel or wicked 3. excessively bad, unpleasant, or difficult Example: fiendish weatherfiendishly adverbfiendishness noun

Merriam-Webster's Collegiate Dictionary