General:
* Critic: This is a broad term for someone who expresses disapproval or negative opinions.
* Opponent: This term suggests someone who actively opposes a specific person, idea, or policy.
* Dissenter: This term implies a disagreement with a prevailing view or authority.
* Protestor: This refers to someone who publicly expresses disapproval or opposition, often through demonstrations or rallies.
More specific:
* Activist: This describes someone who takes action to bring about social or political change, often through advocacy or campaigning.
* Reformer: This refers to someone who seeks to improve or change existing systems or institutions.
* Whistleblower: This describes someone who exposes wrongdoing or illegal activity within an organization or government.
* Debater: This refers to someone who engages in reasoned argument and discussion.
* Sceptic: This describes someone who doubts or questions claims or beliefs.
Negative connotations:
* Detractor: This term implies someone who is consistently critical and negative.
* Malcontent: This describes someone who is dissatisfied and inclined to complain.
* Rebel: This suggests someone who opposes authority or established rules.
* Heretic: This refers to someone who holds beliefs that are considered unorthodox or dangerous.
The best word to use depends on the specific situation and the intended meaning. Consider the context, the severity of the opposition, and the tone you want to convey.