unholy vs diabolical

unholy and diabolical both are adjectives.

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

As adjectives, unholy and diabolical are synonyms defined as:

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

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

unholy (adjective)	diabolical (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