The Pope
Early on in the developement of Christianity, churches had a great deal of power, and in turn the Bishops of those churches also had a lot of power. This power that they possessed was reffered to as Petrine Supremacy. Many early Bishops believed that they were the successors of Peter, who was said to have been given the keys to the kingdom of heaven by Jesus. At the end of the 4th century bishops were attempting to use their title of papa, or later pope, in ways, like Pope Leo I (440-461) did. He used the title of Petrine Supremacy to present himself as the heir of Peter, who was also chosen by Jesus to be the head of the Church. While the Bishops had so much power, state officials were still claiming some amounts of power over the church.