Disclaimer: I do not own the Ender's Game series, any of its plots, or any of its character.
After Valentine left, Peter rethought. He'd never realized how much he'd come to rely on her after all these years. He'd always thought of it as using her: he was the puppeteer and she the marionette. And if that included allowing her to use him too, well, that was only fair. He always made it a part of his plan, like with the squirrels. He'd never forget the look of sheer horror on his parents' faces after they'd seen him, the real him, exposed before them. But he'd worked it into his plan, played perfectly the part of the struggling sociopath. He always had a plan, Peter. But what good was a plan without Valentine, his voice of reason, his counterpart, the Demosthenes to his Locke? Maybe she'd influenced him more than he'd meant her to. He only meant to learn enough from her to feign compassion, fake concern, adopt a clear and concise voice, one that people could sympathize with. And it worked. The people loved him. He was practically already the next Hegemon. The entire world, in one great chunk, was all under his control. But something was still missing: the girl beside him.
Of course Valentine would leave to be with Ender. It was the obvious choice. He was the savior of the universe, the broken, the imperfect, the struggling, the compassionate hero, her younger brother. He was the one she protected from Peter, the frightening, the manipulative, the power-hungry, the incapable-of-love villain. But there was one thing she had gotten wrong, one thing that she had never believed about him, one thing he'd never expect her to. He wasn't incapable of love. He'd loved her. But she was gone. So he carried on with his plans. He became the next and the last Hegemon, the ruler of the world. He had all the power in the world, and he was a good leader. The people loved him. Sure, he made mistakes. Sure, sometimes he still reverted to that boy who would skin squirrels alive for the pleasure of watching them squirm. He was still Peter, after all. And, wherever she was, she was still Valentine. He knew when the book came out, when it was passed along quietly, without mention, without discussion, when it changed the way of life on earth, who wrote it. He knew his siblings too well not to. He knew Valentine too well. So he contacted them. He asked Ender to write down the story of his life, of his mistakes, of his triumphs. He wanted the world to know who he truly was and who he became, but most of all, he wanted Valentine to.
Some would say that Graff lost his edge after the Third Invasion, lost his near-perfect ability to shape people and make them successful. He could no longer take children and make soldiers. He especially lost all reputation when he came under trial for the last soldier he'd made. Ender's success nearly ruined his life. And the charges were true, certainly: mistreatment of children, yes, after what he'd done to make Ender what he had become; negligent homicide, of course, he'd stood by while Ender had unknowingly killed Stilson and Bonzo. But look where it had gotten them. Nobody on earth would have even been alive to prosecute him if it wasn't for Ender and everything Graff had made him. But the truth of it, the reason that Graff had lost the ability to take a piece of wood and carve it ever so precisely into a masterpiece, was that he simply didn't want to. He was sick of it. He was sick of prodding the kids, of forcing them into what the adults wanted them to be. Ender had been his breaking point.
He'd seen what it had done to him. Ender had collapsed from exhaustion, had pleaded to quit several times, had refused to continue until they'd dragged Valentine in to straighten him out. He'd ignored it, justified it as the simple cost of winning a war. And Ender had saved the world. He'd become everything Graff had forced him to be. He was broken, he was tired, but he was a hero because of Graff, because, as much as he'd never realized, Graff had always been behind the scenes, tugging a string here or there to spark a reaction he knew would come. And Graff was proud of him. But he was also disgusted. He'd taken a sweet kid and made him a harsh warrior. What would have happened if Graff had just left him alone? Would he have had a chance at happiness, unlike now? He'd saved the world, but at the cost of himself. And Graff saw it. Just like the school had spent Ender's ambition, all these years had spent his. He'd tried a different job, at first, Minister of Colonization. He'd quit pretty quickly. Just like Ender, he could have spent forever at the lake.