unbelievingly vs unbelieving

unbelievingly is not an adjective while unbelieving is an adjective.

Word	Noun	Adjective	Verb	Adverb
unbelievingly	No	No	No	Yes
unbelieving	No	Yes	No	No

unbelievingly (adjective)	unbelieving (adjective)
	holding that only material phenomena can be known and knowledge of spiritual matters or ultimate causes is impossible
	denying or questioning the tenets of especially a religion
	rejecting any belief in gods

unbelievingly (adverb)	unbelieving (adverb)
in an incredulous manner