Nouns

(n)faultfinding, carpingpersistent petty and unjustified criticism

Adjectives

(s)faultfindingtending to make moral judgments or judgments based on personal opinions“a counselor tries not to be faultfinding”
(s)captious, faultfindingtending to find and call attention to faults“a captious pedant”, “an excessively demanding and faultfinding tutor”