St. Agapetus I
Agapetus · 535 – 536
Traveled to Constantinople on a diplomatic mission and ended up deposing a heretical patriarch before dying far from home.
Agapetus was a Roman aristocrat, the son of a priest who had been killed during riots. He was sent to Constantinople by the Ostrogothic king Theodahad to negotiate with Emperor Justinian. While there, he discovered that the patriarch Anthimus held Monophysite views. Agapetus refused to celebrate the Eucharist with him, convinced Justinian to remove Anthimus, and personally consecrated a new patriarch. He died in Constantinople shortly after, never making it home to Rome.
Standing Up to an Emperor
Agapetus arrived in Constantinople as a diplomat and left as a reformer. When he realized the patriarch was a Monophysite, he didn't politely look the other way. He told the most powerful man in the world that the patriarch had to go, and Justinian listened. It cost Agapetus nothing less than his life, since he died there before he could return.