A rebel.
A traitor
A person who speaks out against something is often referred to as a critic, dissenter, or opponent.
1. Call an ambulance2. Call the police and bring charges against that person.
A traitor.
Abolitionist -- they were in favor of abolishing slavery.
Protagonist
A person who goes against the flow (of society, their community, their established culture, and so on) might be called a nonconformist.
A bacteriologist.
Proponents of Enlightenment
When one person plays chess against many opponents at the same time is called a simul.
Defector, Traitor, Double Agent.
Nativist