Pope  LEO   I
c.399 - 461

Saint Leo I, the Great, was perhaps the first authentic pope and is some-times called the 'father of papacy'.

During the pontificate of pope Leo the western Roman Empire disintegrated and in the East theological differences with the Roman church flared up.

Leo I successfully enforced his authority by declaring that papal power was granted by Christ to St.Peter alone, and that power was passed on by Peter to his successors in Rome.

Leo further enhanced the prestige of the papacy when he persuaded the Huns not to attack Rome, and the Vandals not to destroy Rome when they occupied it three years later.

www link :
From the Catholic Encyclopedia:

The Petrine Doctrine

Pope Leo and Attila