Source : WordNet®

mephistophelean
     adj : 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" [syn: {devilish}, {diabolic}, {diabolical}, {mephistophelian}]