blunderer vs sad sack

blunderer and sad sack both are nouns.

Word	Noun	Adjective	Verb	Adverb
blunderer	Yes	No	No	No
sad sack	Yes	No	No	No

As nouns, blunderer and sad sack are synonyms defined as:

blunderer and sad sack: someone who makes mistakes because of incompetence

Other synonyms of blunderer include botcher, bumbler, bungler, butcher, fuckup, fumbler, stumbler.

blunderer (noun)	sad sack (noun)
someone who makes mistakes because of incompetence	someone who makes mistakes because of incompetence