bungler vs sad sack

bungler and sad sack both are nouns.

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

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

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

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

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