disregardless vs no matter

disregardless and no matter both are adverbs.

Word	Noun	Adjective	Verb	Adverb
disregardless	No	No	No	Yes
no matter	No	No	No	Yes

As adverbs, disregardless and no matter are synonyms defined as:

disregardless and no matter: in spite of everything; without regard to drawbacks

Other synonyms of disregardless include disregarding, irrespective, regardless.

disregardless (adverb)	no matter (adverb)
in spite of everything; without regard to drawbacks	in spite of everything; without regard to drawbacks