a person who held beliefs going against the teachings of a church.
A heretic believed in other beliefs and spoke about those beliefs to be labeled. Heretics have historically been treated with force, violence, and punishment for their beliefs.
A famous heretic is Martin Luther who wrote the 95 Theses criticizing the Catholic Church and their practice of selling indulgences. His beliefs would lead to the Reformation, splitting of the Catholic Church into Protestant faiths. A violent reaction to heretics is the Inquisition which used torture to find people guilty of heresy or speaking out against the Church.