der Besserwisser — someone who always believes he knows better
der Klugscheißer — vulgar: someone who thinks himself very clever and believes his remarks are very clever
oberlehrerhaft — know-it-all and lecturing, like an old-style senior schoolmaster
The dictionary DWDS marks all three as disparaging. A correction that serves the work is welcome. These words are for a correction that mainly serves the person who makes it.