mephistophelean

adjectives

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"
devilish, diabolic, diabolical, mephistophelean, mephistophelian
is derived from
Mephistopheles