Open English Wordnet
Adjectives
(s)devilish, diabolic, diabolical, mephistophelian, mephistopheleanshowing 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”
Adverbs
(r)devilishly, devilishin a playfully devilish manner“the socialists are further handicapped if they believe that capitalists are not only wicked but also devilishly clever”