ne'er-do-well vs do-nothing

ne'er-do-well and do-nothing both are nouns.

Word	Noun	Adjective	Verb	Adverb
ne'er-do-well	Yes	No	No	No
do-nothing	Yes	Yes	No	No

As nouns, do-nothing is a hypernym of ne'er-do-well; that is, do-nothing is a word with a broader meaning than ne'er-do-well:

Other hypernyms of ne'er-do-well include bum, idler, layabout, loafer.

ne'er-do-well (noun)	do-nothing (noun)
an idle worthless person	person who does no work

ne'er-do-well (adjective)	do-nothing (adjective)
	characterized by inability or unwillingness to work toward a goal or assume responsibility