complainer vs sniveller

complainer and sniveller both are nouns.

Word	Noun	Adjective	Verb	Adverb
complainer	Yes	No	No	No
sniveller	Yes	No	No	No

As nouns, complainer and sniveller are synonyms defined as:

complainer and sniveller: a person given to excessive complaints and crying and whining

Other synonyms of complainer include bellyacher, crybaby, grumbler, moaner, squawker, whiner.

complainer (noun)	sniveller (noun)
a person given to excessive complaints and crying and whining	a person given to excessive complaints and crying and whining