diabolical

dʌɪəˈbɒlɪk(ə)l

adjective

characteristic of the Devil, or so evil as to be suggestive of the Devil.

his diabolical cunning

devilish,diabolic,fiendish,satanic,Mephistophelian,demonic,demoniacal,hellish,infernal,evil,wicked,ungodly,unholy,cacodemonic