unquestionable vs authentic

unquestionable and authentic both are adjectives.

Word	Noun	Adjective	Verb	Adverb
unquestionable	No	Yes	No	No
authentic	No	Yes	No	No

As adjectives, unquestionable and authentic are synonyms defined as:

Other synonyms of unquestionable include bona fide, veritable.

unquestionable (adjective)	authentic (adjective)
incapable of being questioned	not counterfeit or copied
not counterfeit or copied	conforming to fact and therefore worthy of belief
not open to question