sinful vs unholy

sinful and unholy both are adjectives.

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

As adjectives, sinful and unholy are synonyms defined as:

Other synonyms of sinful include wicked.

sinful (adjective)	unholy (adjective)
far more than usual or expected	not hallowed or consecrated
having committed unrighteous acts	extremely evil or cruel; expressive of cruelty or befitting hell
characterized by iniquity; wicked because it is believed to be a sin	having committed unrighteous acts