diabolic
1. [ adjective ] showing the cunning or ingenuity or wickedness typical of a devil
Synonyms: devilish mephistophelean mephistophelian diabolical
Examples:

"devilish schemes" "the cold calculation and diabolic art of some statesmen" "the diabolical expression on his face" "a mephistophelian glint in his eye"

Related terms: evil
2. [ adjective ] extremely evil or cruel; expressive of cruelty or befitting hell
Synonyms: satanic fiendish unholy infernal hellish diabolical demonic
Examples:

"something demonic in him" "fires lit up a diabolic scene" "a fiendish despot" "hellish torture" "infernal instruments of war" "satanic cruelty" "unholy grimaces"

Related terms: evil
Similar spelling:   diabolical
  diabolize
  diabolist
  diabolism
  diabolise
  Diblasi