"Αυτός έγραψε μια θετική κριτική."

"he wrote a positive critique" is currently marked as incorrect; "he wrote a positive critic" is given as a correct translation (which it isn't).

Θα μπορουσαμε να το πουμε με χρηση βοηθητικου ρηματος Ηe did writte a positive review.