| grumble |
| libellant |
| litigator |
| opponent(noun, enemy, censor, detractor) |
| squawk(noun, person, complaint, delation) |
| aristarch(noun, opponent, enemy, attacker, critic) |
| attacker(noun, opponent, enemy, critic, defamer) |
| backseat driver(noun, expression, opponent, enemy, attacker) |
| belittler(noun, opponent, enemy, attacker, critic) |
| carper(noun, opponent, enemy, attacker, critic) |
| caviler(noun, opponent, enemy, attacker, critic) |
| censor(noun, opponent, enemy, attacker, critic) |
| censurer(noun, opponent, enemy, attacker, critic) |
| critic(noun, opponent, enemy, attacker, censor) |
| defamer(noun, opponent, enemy, attacker, critic) |
| disparager(noun, opponent, enemy, attacker, critic) |
| disputer(noun, opponent, enemy, attacker, critic) |
| doubter(noun, opponent, enemy, attacker, critic) |
| fretter(noun, opponent, enemy, attacker, critic) |
| hypercritic(noun, opponent, enemy, attacker, critic) |