scum bag vs dirty dog

scum bag and dirty dog both are nouns.

Word	Noun	Adjective	Verb	Adverb
scum bag	Yes	No	No	No
dirty dog	Yes	No	No	No

As nouns, scum bag and dirty dog are synonyms defined as:

scum bag and dirty dog: a person who is deemed to be despicable or contemptible

Other synonyms of scum bag include bum, crumb, git, lowlife, puke, rat, rotter, scumbag, skunk, so-and-so, stinker, stinkpot.

scum bag (noun)	dirty dog (noun)
a person who is deemed to be despicable or contemptible	a person who is deemed to be despicable or contemptible