June 26 - 1409 - Alexander V is Crowned Pope
Alexander V was installed as Pope to end the Western Schism after the Council of Pisa, where there were two different Popes with two different power bases. All Alexander's coronation did was make there be three different Popes with three different power bases. Yet the new, more absurd situation helped lead to a resolution to the Western Schism. Unfortunately for Alexander, it came after he passed away in 1410, and was only successfully achieved with a whole other Council at the city of Constance.
Note: Apologies for the background noise.