faultfinder
[noun]
Synonyms: critic, aristarch, carper, caviler, criticizer, knocker, momus, smellfungus, Zoilus, grouch, bellyacher, complainer, crab, griper, grump, kicker, malcontent, sorehead, sourpuss

[TahlilGaran] English Synonym Dictionary ▲

fault·find·er (fôltfīndər)
n.
One who is given to petty criticism and constant complaint.

[TahlilGaran] American Dictionary ▲