A/N: in this story, italics are not used to emphasise certain words, but rather to indicate the distinction between the two different characters where it might get confusing otherwise.
It was the summer of 1898. He was feeling bored. His parents had died the year prior and he now had the care for his younger brother and sister. He wanted to be at Hogwarts, wanted to do research and discuss magical problems with the greatest wizards of all time. But instead, he was trapped here, in Godric's Hollow. Stupid, lame, boring Godric's Hollow.
Until he met him. So brilliant, so cunning, with a mind so sharp, … and so very, very, attractive with his wavy blond hair. He had come to stay with his aunt Mathilda, who was their neighbour. They soon found out that they shared a lot of interests and it was refreshing to be able to talk to someone at his own level again. They spent hours on either attic room, trying out formulas and discussing politics. Even though they were only a window apart, they used to write each other letters all the time.
Then, one evening, he suggested that wizards should rule the world. It made him think. Perhaps that really was the right way. After all, wizards knew more than Muggles did, so wouldn't it make sense if the most knowledgeable looked after the less fortunate? He didn't see any harm in it then. Neither did he see any harm in kissing him, one starlit night when they had been working for hours, nor in kissing him again the next time he saw him. He also didn't see any harm when he wanted to rule Muggles in a dictatorial rather than a democratical way. Because he was his friend and he only wanted the best, right? Or that's what he had wanted to believe, pushing aside any thoughts of doubt. Sure, some would fall, but that was inevitable, wasn't it? It was all for the greater good.
He had laughed when he had kissed him, feeling like he could take on the world. Which they would, sooner rather than later if it were up to him. They were one and the same, one mind and one soul in two bodies. Sometimes he could not even remember where he ended and he began, but that was okay.
But then there had been that fight. That horrible, horrible fight that was still causing him nightmares. Ariana had died that night. Wonderful, sweet Ariana, who he had been neglecting in order to be with him. Oh, how he regretted it then. He had said that it didn't matter, because it was all for the greater good. How would he know? He never had any siblings. He ran, terrified of the consequences and he had to live with it for the rest of his live. Why couldn't he have died instead of Ariana?
When he rose to power, using the line they'd come up with when they were seventeen as a way to kill of Muggles at random, he tried to ignore the rapports. Surely he couldn't be behind all these murders? But after a while, the evidence piled up and the call for him to do something about it grew stronger and stronger. He tried reasoning with him, but to no use. Muggles were nothing better than the dirt under their shoes and they had to be killed to accept his superiority. It was really all for the Greater Good. He did not agree, of course not. So he had to step in. He had to be the one to defeat him, even though part of him had never stopped loving him. He had to do it, for the greater good.
They had stood opposite one another, he was challenging him. He once more tried reason, appealing on his good side, on the love they had shared. He had only laughed. There had never been love, not from his part at least. It had been so easy to manipulate him. He had used him, for the greater good. He realised that his love and his reluctance to act had nearly caused the downfall of the world as he knew it.
As the curse hit Gellert Grindelwald in the chest, Albus Dumbledore swore that he would never fall in love again. It was better for the world if he didn't. It was all really for the greater good.