niggler vs critic

niggler and critic both are nouns.

Word	Noun	Adjective	Verb	Adverb
niggler	Yes	No	No	No
critic	Yes	No	No	No

As nouns, critic is a hypernym of niggler; that is, critic is a word with a broader meaning than niggler:

niggler: someone who constantly criticizes in a petty way
critic: someone who frequently finds fault or makes harsh and unfair judgments

niggler (noun)	critic (noun)
someone who constantly criticizes in a petty way	a person who is professionally engaged in the analysis and interpretation of works of art
	anyone who expresses a reasoned judgment of something
	someone who frequently finds fault or makes harsh and unfair judgments