1286 - November 26, 1326: Age 40
Hugh Despenser was a nobody, just a landless knight, until he married Eleanor de Clare. Her grandfather, Edward I, owed his father a lot of money, and her hand in marriage was intended to stand in for payment of the debt. It really paid off when the unexpected death of her brother left her an heiress. Despenser suddenly found himself one of the richest men in the kingdom. Moreover his status as the nephew-in-law to the new king Edward II, who succeeded his father in 1307, gave him personal access to the sources of power in the kingdom.
Wealth: check. Power: check. What was next? More wealth and power, and as much vicious pleasure as he could squeeze out of life. Hugh le Despenser the Younger was a complete bastard. He robbed from anyone he could: rich, poor, anyone weaker than himself was fair game. He murdered hostages who didn't pay their ransom. He even had a noblewoman tortured to force her to hand over her lands. But his worst crime, in the eyes of the English aristocracy, was that he became the King's lover. Edward II was weak, unintelligent, and gay. Hugh le Despenser took full advantage of those qualities, and made himself the most hated man in Europe.
When the English barons forced Edward II to exile le Despenser, he became a pirate in the English Channel. When he returned the next year he once again became the favourite of the king and worst enemy of everyone else, especially the Queen. When she succeeded in deposing the King in 1326, le Despenser was captured.
He tried to starve himself before his trial but was unsuccessful. He was tried on a number of charges, found guilty, and sentenced to death by hanging, drawing and quartering. He was dragged to the execution site behind four horses, hung until nearly dead, then tied to a high ladder where the executioner cut off his genitals and cut out his entrails, throwing them on a fire below. Then he was taken down and beheaded. His body was cut into four pieces, each piece being displayed in a different city, and his head was mounted on the gates of London. Apparently the Queen was picnicking with her boyfriend on the execution grounds while all this was being done. It is also mentioned that le Despenser "suffered with great patience, begging forgiveness from the bystanders."
Sources: Wikipedia, Edward II (blog), Chronicle