couch potato vs do-nothing

couch potato and do-nothing both are nouns.

Word	Noun	Adjective	Verb	Adverb
couch potato	Yes	No	No	No
do-nothing	Yes	Yes	No	No

As nouns, do-nothing is a hypernym of couch potato; that is, do-nothing is a word with a broader meaning than couch potato:

couch potato: an idler who spends much time on a couch (usually watching television)
do-nothing: person who does no work

Other hypernyms of couch potato include bum, idler, layabout, loafer.

couch potato (noun)	do-nothing (noun)
an idler who spends much time on a couch (usually watching television)	person who does no work

couch potato (adjective)	do-nothing (adjective)
	characterized by inability or unwillingness to work toward a goal or assume responsibility