knocker vs faultfinder

knocker and faultfinder both are nouns.

Word	Noun	Adjective	Verb	Adverb
knocker	Yes	No	No	No
faultfinder	Yes	No	No	No

As nouns, faultfinder is a hypernym of knocker; that is, faultfinder is a word with a broader meaning than knocker:

Other hypernyms of knocker include cynic.

knocker (noun)	faultfinder (noun)
a device (usually metal and ornamental) attached by a hinge to a door	someone who is critical of the motives of others
either of two soft fleshy milk-secreting glandular organs on the chest of a woman
one who disparages or belittles the worth of something
a person who knocks (as seeking to gain admittance)
(Yiddish) a big shot who knows it and acts that way; a boastful immoderate person