Read the dictionary definition of diabolical. All definitions for this word.
1. extremely evil or cruel; expressive of cruelty or befitting hell
1. something demonic in him--something that could be cruel
2. fires lit up a diabolic scene
3. diabolical sorcerers under the influence of devils
4. a fiendish despot
5. hellish torture
6. infernal instruments of war
7. satanic cruelty
8. unholy grimaces
2. showing the cunning or ingenuity or wickedness typical of a devil
1. devilish schemes
2. the cold calculation and diabolic art of some statesmen
3. the diabolical expression on his face
4. a mephistophelian glint in his eye