In an Instant
Everything can change in an instant. In an instant, life becomes death, peace is replaced by fear, children lose their innocence. He had seen it happen, time and time again. It had been the same in the First War, and when Harry had emerged from the maze, clutching the body of Cedric Diggory, he knew it would be the same again.
At the moment when Severus Snape was stood before him, with his face distorted by hatred, both at himself, for what he is about to do, and hatred at Albus for making him perform this life-changing act, Albus knew, he just knew that his death marked another change. With him gone, Tom would think himself unstoppable. "Severus, please." He pleaded. Please, end this now. Protect the castle. Protect the students. Keep Harry safe. Let me die.
As the green light flew towards him, Albus couldn't help but feel relieved. He had lived a long life, a life full of regrets, and in his final moments he allowed himself to reflect on them, hoping his rights had begun to make up for his wrongs. Ariana. His biggest regret. At that terrible moment, his whole life had changed in an instant; her life had ended in the blink of an eye. To this day he never knew who had performed the spell that killed her, whether it was himself, Aberforth or him, Gellert. All he knew was he was entirely to blame. He had placed his own, selfish needs before those of his brother, and poor sister, both of whom were dependent on him, needed him. He had allowed himself to be swept along with Gellert's plans, Gellert's dreams, ignoring the people who mattered most. His mother would have been distraught, had she been alive to see what remained of the Dumbledore family; Albus, ashamed and crooked-nosed, and Aberforth, bitter and miserable. Gellert. His second biggest regret. The damage he caused to the world while he, Albus, tried to ignore the pleas of the Wizarding World to intervene, while he, Albus, feared what meeting Gellert again would do to him.
Tom. Another big regret. He had known, when he met Tom in the orphanage that he needed to keep an eye on him at Hogwarts, that even as a child there was something sinister, and twisted about him. And so he watched, hoped, and prayed that being part of the world he was born into would change him, for the better, making him kinder, nicer, more humane. And yet, as the years went by, it became painfully obvious that he would not change, that he was more twisted, and sinister than Albus could possibly have imagined. He should have intervened, Albus had thought upon his resurrection two years previously. But he had not, and now he was dead, and Tom was alive. In an instant, his life had ended, and Tom's continued to wreck havoc through everyone's lives. If Albus had stopped him the first time around, maybe things would be different, maybe there wouldn't be Horcruxes, maybe so many of the dead would still be alive. Maybe Harry Potter would still have parents, a family. Because this is his next regret. The lives of the Potters, James, Lily and Harry. Of Sirius, Remus and Peter. Of Severus. So many people, so many regrets. That night, that fateful Halloween night, everything changed, the lives of everyone in the Wizarding World changed in an instant. Loved ones were lost, friendships ruined, an orphaned child became a hero, an innocent man was condemned, and a Dark Lord was vanished. And now Tom was back, and there would be no Albus Dumbledore to stop him, to help Harry, to protect Hogwarts. Yes, everything can change in an instant, and for the Wizarding World, Harry James Potter, the Chosen One, the Boy Who Lived, became their last hope.