Zancrow
Zancrow hadn't told anyone about it, but his family had died in a fire when he was very young. So young in fact, that watching their house burn right in front of him was his earliest memory. He had been traumatized by the event, developing pyrophobia soon afterwards, shying away from any flame he saw, even if it was from a mere candle.
He had become an orphan of course, and ended up in the town orphanage, living amongst other morose children like himself. He had eventually been adopted by a kind woman with an even kinder daughter, both of whom he had considered "very pretty." When he began living with them, they revealed that they were part of a religion which worshipped gods, and invited him to join them so that those same gods could prevent anything like what happened to him then from happening again.
For a few months, he lived a good life with them. That is, until a gang of magic bandits attacked the town they were living in. He had been a bit aways from the town, gazing up at the afternoon sky, when he began to smell smoke off in the distance. He had looked around to see that the smoke was coming from the direction of the village. Silently praying that it wouldn't be what he thought it was, he ran back toward the village... and saw that his prayers had been spat upon.
The town was aflame, and there were several corpses littering the streets as well. A scene out of Hell to Zancrow, who had witnessed his family being burned alive in their own home. He fiercely denied what he saw in front of him, but it was still there, no matter how much he tried not to believe it. He looked towards the house he lived in, only to see it had already been destroyed, and in the wreckage, he saw the corpses of the two females he was closest to.
Zancrow looked away from the sight, and he saw the bandits. They were on another hill, overlooking what they had accomplished, looking very damn proud of themselves. Zancrow then became embroiled in anger. Anger at both the bandits and the gods. The bandits for destroying what he held close, and the gods for not protecting those close to him. Zancrow ran at the bandits, the air around him beginning to get hotter as he closed the distance between himself and them. When he finally reached them, fire blazed out of nowhere, consuming anything that he unconsciously commanded it to. He destroyed the bandit gang completely, leaving nothing but ashes and charred bones. Zancrow then passed out.
It was night when Zancrow awoke once more, the stars shining brightly. Initially, he became panicked that his foster mother and sister were worried about him, then he smelled the lingering scent of smoke in the air and remembered everything that had happened, including his newfound ability to use Fire Magic. Zancrow cursed the gods for not protecting his family, and for cursing him with the power to use fire, the very thing that had robbed him of his family in the first place. He decided right then and there that he would kill the gods, no matter what. It was also the moment that he began to slowly lose his sanity.
It wasn't long until Zancrow met Hades, and subsequently joined Grimoire Heart. It was in that same guild that Zancrow discovered the existence of God Slayer Magic. Naturally, Zancrow immediately decided to learn Flame God Slayer Magic, so that he could never have to fear another flame ever again. And when Grimoire Heart reached the Ultimate World of Magic, Zancrow would be strong enough to finally kill the gods and exact his vengeance upon them.
Fairy Tail belongs to the brilliant Hiro Mashima and not myself.