Final answer:
Key Popes associated with the 16th-century Reformation include Pope Leo X, who excommunicated Martin Luther, and Pope Paul III, who initiated the Counter-Reformation. Pope Alexander VI's earlier corrupt papacy also played an indirect role by contributing to the call for reform.
Step-by-step explanation:
The question asks about the role of the Popes during the Reformation in the 16th century. The Reformation, initiated by Martin Luther's 95 theses in 1517, began as a movement to address the corruption and issues within the Catholic Church, such as simony, nepotism, and the worldly involvement of the clergy. Pope Leo X, who excommunicated Luther, and Pope Paul III, who convened the Council of Trent, were two central figures. Pope Alexander VI's papacy, characterized by nepotism and corruption, also added to the urgency for reform despite being earlier.
Thus, pivotal Popes central to the Reformation included Pope Leo X, who was in office when Luther made his objections known, and Pope Paul III, who formally addressed some of these concerns during the Counter-Reformation. Pope Alexander VI, through his notorious papacy, also indirectly contributed to the urgency for reform that culminated in the Reformation. Their collective contribution demonstrates a complex intertwining of religious and political power that had significant consequences for the trajectory of Christianity in Europe.