unholy vs diabolic

unholy and diabolic both are adjectives.

Word	Noun	Adjective	Verb	Adverb
unholy	No	Yes	No	No
diabolic	No	Yes	No	No

As adjectives, unholy and diabolic are synonyms defined as:

unholy and diabolic: extremely evil or cruel; expressive of cruelty or befitting hell

Other synonyms of unholy include demonic, diabolical, fiendish, hellish, infernal, satanic.

unholy (adjective)	diabolic (adjective)
not hallowed or consecrated	extremely evil or cruel; expressive of cruelty or befitting hell
extremely evil or cruel; expressive of cruelty or befitting hell	showing the cunning or ingenuity or wickedness typical of a devil
having committed unrighteous acts