A leader is someone who guides or directs others towards a common goal or purpose. In this context, it refers to an individual who played a prominent role in leading or spearheading a particular movement or organization.
Martin Luther: As one of the key figures of the Protestant Reformation, Martin Luther led efforts to challenge certain practices and beliefs within the Roman Catholic Church.
Pope Paul III: He was one of the most influential popes during the time of the Catholic Reformation; he called for important church reforms and convened the Council of Trent.
St. Ignatius Loyola: Founder of the Jesuit order, Ignatius Loyola played a significant role in leading and organizing the Catholic efforts during the Counter-Reformation.