From (double!) coronation to abdication, a terrible pontificate, with far-reaching dangerous consequences - from the biography of Pope Saint Celestine V (Peter Celestine - Pietro da Murrone), who died on May 19, 1296:
In reply to the request of the cardinals, that he should come to Perugia to be crowned, Pietro, at the instigation of Charles, summoned the Sacred College to meet him at Aquila, a frontier town of the Kingdom of Naples. Reluctantly they came, and one by one, Gaetani being the last to appear. Seated on an humble ass, the rope held by two monarchs, the new pontiff proceeded to Aquila, and, although only three of the cardinals had arrived, the king ordered him to be crowned, a ceremony which had to be repeated in traditional form some days later, the only instance of a double papal coronation. Cardinal Latino was so grief-stricken at the course which affairs were evidently taking that he fell sick and died. Pietro took the name of Celestine V. Urged by the cardinals to cross over into the States of the Church, Celestine, again at the behest of the king, ordered the entire Curia to repair to Naples. It is wonderful how many serious mistakes the simple old man crowded into five short months. We have no full register of them, because his official acts were annulled by his successor. On the 18th of September he created twelve new cardinals, seven of whom were French, and the rest, with one possible exception, Neapolitans, thus paving the road to Avignon and the Great Schism. Ten days later he embittered the cardinals by renewing the rigorous law of Gregory X, regulating the conclave, which Adrian V had suspended. He is said to have appointed a young son of Charles to the important See of Lyons, but no trace of such appointment appears in Gams or Eubel. At Monte Cassino on his way to Naples, he strove to force the Celestine hermit-rule on the monks; they humoured him while he was with them. At Benevento he created the bishop of the city a cardinal, without observing any of the traditional forms. Meanwhile he scattered privileges and offices with a lavish hand. Refusing no one, he was found to have granted the same place or benefice to three or four rival suitors; he also granted favours in blank. In consequence, the affairs of the Curia fell into extreme disorder. Arrived in Naples, he took up his abode in a single apartment of the Castel Nuovo, and on the approach of Advent had a little cell built on the model of his beloved hut in the Abruzzi. But he was ill at ease. Affairs of State took up time that ought to be devoted to exercises of piety. He feared that his soul was in danger. The thought of abdication seems to have occurred simultaneously to the pope and to his discontented cardinals, whom he rarely consulted.
Some years after his canonization by Clement V in 1313, his remains were transferred from Ferentino to the church of his order at Aquila, where they are still the object of great veneration. His feast is celebrated on 19 May. (Catholic Encyclopedia)
Wait a second: he was canonized just 17 years after his death? Now, there is a process ripe for reexamination.