Dumbledore and Grindelwald were not only the most talented wizards of their time, but likely of all times. It then comes as no surprise that when they finally met again, they engaged in a duel that eyewitnesses have stated it was the greatest duel the Wizarding World had ever seen. With their skills, might, the feelings from their past, and the Elder Wand in the mix, it all made for a match of epic proportions.
Yet, at the end of it all, the Elder Wand itself could not save Grindelwald as Dumbledore's skills managed to outshine his and lead to the final loss of the Dark Wizard.
Dumbledore would bring the captured Grindelwald before the Wizarding World's authorities, to decide his fate. To add salt to injury, Grindelwald would then be imprisoned in the prison he himself built, Nurmengard. The topmost cell of grim fortress would be assigned as his residence for the remainder of his life. Dumbledore would keep the Elder Wand for himself.
Having defeated the person who was considered the most powerful Dark Wizard who had roamed the Wizarding World, Albus Dumbledore was celebrated worldwide as a hero. The Ministry of Magic gave Dumbledore the Order of Merlin (First Class) award for bringing down Gellert and finally putting a stop to his revolution and terror over the world. The award is generally given out for acts of outstanding bravery or distinction in magic.
While it's only one out of many tremendous achievements Albus would eventually accomplish during his lifetime, defeating Grindelwald is certainly one of the main reasons for his fame among the Wizarding Community.
Grindelwald's ultimate demise may have been celebrated worldwide, but his years of terror also received their share of appreciation, from those who favoured the Dark Arts and shared his vision of wizarding dominance over Muggles. One of them would be the next great Dark Wizard, or the Dark Lord himself. Tom Marvolo Riddle, or Lord Voldemort, would set himself on a quest to acquire the Elder Wand and the trail would eventually lead to Gellert Grindelwald, who once possessed the wand.
Roughly fifty-three years after his ultimate fall, still living his days locked in a cell in Nurmengard with just a tiny window, a hard bed and a thin blanket, Grindelwald would wake up to a surprise visitor. Using his magic powers to infiltrate the prison, Voldemort would come to confront Grindelwald for information about the location of the Elder Wand.
Voldemort wasn't quite expecting it to be a confrontation. He was assuming he'd only see surprise and fear from Grindelwald. However, despite the years spent in his very own prison, Grindelwald's spirit wasn't broken. While unarmed and defenceless, and standing in front of the only Dark Wizard considered more powerful than himself, he wasn't going to suddenly offer assistance to someone.
Grindelwald refused to provide any information regarding the Elder Wand's location, and instead taunted Voldemort by name and laughed at his desire for the wand. Voldemort, both shocked and annoyed by the behaviour he was met with, was growing full with rage. The tipping point would be Grindelwald saying he could kill him but the Elder Wand would never ever truly belong to him. Having gotten nothing but arrogance from Grindelwald, Voldemort used the Killing Curse to end Grindelwald's life.
Whether he had any else with him in Nurmengard, at that time, or what thoughts were running in his head during all those years, remains unknown. Needless to say, after his imprisonment the general Wizarding World was not preoccupied with Gellert Grindelwald. Due to his actions there was only one thing people cared in relation to him --- that he remains away.
"They say he showed remorse in later years, alone in his cell at Nurmengard. I hope that is true. I would like to think that he did feel the horror and shame of what he had done." ~ Albus Dumbledore