Pertaining to the devil; resembling, or appropriate, or appropriate to, the devil; devilish; infernal; impious; atrocious; nefarious; outrageously wicked; as, a diabolic or diabolical temper or act.(adjective)
source: webster1913
adjective satellite (s)
showing the cunning or ingenuity or wickedness typical of a devil(adj.all)
Example: The cold calculation and diabolic art of some statesmen.
The diabolical expression on his face.