Criticizer and Opponent

Criticizer noun - A person given to harsh judgments and to finding faults.

Opponent and criticizer are semantically related. In some cases you can use "Opponent" instead a noun "Criticizer".

Opponent noun - One that takes a position opposite another in a competition or conflict.

Criticizer and opponent are semantically related. Sometimes you can use "Criticizer" instead a noun "Opponent".