scum bag vs so-and-so

scum bag and so-and-so both are nouns.

Word	Noun	Adjective	Verb	Adverb
scum bag	Yes	No	No	No
so-and-so	Yes	No	No	No

As nouns, scum bag and so-and-so are synonyms defined as:

scum bag and so-and-so: a person who is deemed to be despicable or contemptible

Other synonyms of scum bag include bum, crumb, dirty dog, git, lowlife, puke, rat, rotter, scumbag, skunk, stinker, stinkpot.

scum bag (noun)	so-and-so (noun)
a person who is deemed to be despicable or contemptible	a person who is deemed to be despicable or contemptible