1. (计划、行动、装置等)巧妙的，富有想象力的
A fiendish plan, action, or device is very clever or imaginative.

1. extremely evil or cruel
expressive of cruelty or befitting hell

e.g. something demonic in him--something that could be cruel
fires lit up a diabolic scene
diabolical sorcerers under the influence of devils
a fiendish despot
hellish torture
infernal instruments of war
satanic cruelty
unholy grimaces

Synonym: demonicdiabolicdiabolicalhellishinfernalsatanicunholy