Fight Fire With Fire and Burn the Whole World Down

Alone and beaten, Harry resorts to desperate measures in the war with Voldemort and his forces. There was no low, no evil his enemies wouldn't resort to. And so he saw fit to dive straight to the bottom and create a horcrux of his own. That was how it started, that's how the end of the wizarding world began. Two immortal dark lords duking it out was just too much.