hellish vs unholy

hellish and unholy both are adjectives.

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

As adjectives, hellish and unholy are synonyms defined as:

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

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

hellish (adjective)	unholy (adjective)
extremely evil or cruel; expressive of cruelty or befitting hell	not hallowed or consecrated
(informal) very unpleasant	extremely evil or cruel; expressive of cruelty or befitting hell
	having committed unrighteous acts