decidedly vs unquestionably

decidedly and unquestionably both are adverbs.

Word	Noun	Adjective	Verb	Adverb
decidedly	No	No	No	Yes
unquestionably	No	No	No	Yes

As adverbs, decidedly and unquestionably are synonyms defined as:

Other synonyms of decidedly include by all odds, definitely, emphatically, in spades.

decidedly (adverb)	unquestionably (adverb)
without question and beyond doubt	without question
	without question and beyond doubt