Even though he won the Nobel Peace Prize, I don't think John Hume has been properly recognised for what he did in bringing about the end of the Troubles, which was one of the world's most intractable conflicts and could have gone on for generations more.
While others deserve credit (Mo Mowlam, Bertie Ahern, John Major, David Trimble, and yes even Gerry Adams and Martin McGuinness), it was really Hume's achievement, the result of years of hard, thankless and often dangerous work (he was on loyalist hit lists for years, the IRA discussed assassinating him and at one point firebombed his house) in establishing a dialogue with Sinn Fein when the British and Irish political establishments were insisting that they wouldn't talk to them until the IRA laid down its arms.
It was Hume who was the go-between, who was dogged and sometimes virtually alone in his belief that a political solution could be found, and would only be found through dialogue.
I think this came from his deep understanding of the mindset that drove the IRA, and his knowledge that Republicans were as sick of the conflict as everyone else. They were looking for a reason to end it (as were the Loyalists), but the 'sunk cost' fallacy made the price of surrender too high. Hume managed to persuade the British that they needed to offer the Provos a way to save face, to make it look like they weren't surrendering but striking a deal, which meant that their 25 year paramilitary war hadn't just been a pointless waste of life (which it definitely was).
He was that rare combo: a brilliant politician, and a brave, humane and principled man.