Pope John XII lived a life of vices, from gambling to theft to sex, and he also died by them. A husband who found the pope having sex with his wife is said to have beaten him to death.

St. Peter was driven out of Rome by the Emperor Nero, who hated Christians and had issued an order for his arrest. While outside of the city, St. Peter saw a vision of Jesus and decided to return to the city as a martyr. He asked to be crucified, but turned on his head so he would not imitate Jesus's death.

Pope St. Clement I was tied to an anchor and thrown into the Black Sea after he converted his fellow prisoners in a stone quarry to Christianity. It was said the pope struck the ground with an ax and found water to quench the weary workers' thirst. The miracle made the men into believers, but sealed the pontiff's fate.

The death of Pope John Paul I sparked conspiracy theories that the pontiff could have been poisoned, however they were never proven. On the morning of Sept. 29, 1978, 33 days after he was named pope, John Paul I was found dead in his bed. The Vatican reported the 65-year-old pope had likely died of a heart attack, and foul play has never been proven.

Pope St. Stephen I was sitting on his throne and holding mass when the emperor's men stormed into the room and beheaded him, according to The Golden Legends, a collection of hagiographies published in Medieval times.

The year after Pope St. Stephen I was beheaded, the same fate awaited Pope St. Sixtus II. He was one of of several popes to put up with Roman persecution and die a martyr.

Pope John VIII is remembered as one of the greatest popes who met the cruelest of deaths. One of the pontiff's relatives, who reportedly wanted to steal his fortune, tried to poison him. The drug was slow to work, prompting the frustrated relative to bash his head in with a hammer.