The war of the three brothers

Dark/Grey Harry AU: Having grown up with a horcrux as a scar, Voldemorts powers and [to some extent] personality have transferred into Harry. Instead of siding with either Riddle or Dumbledore, Harry becomes a threat in his own right, and soon the three become locked in a war that shakes the core of wizarding Britain. Who will come out on top? [Harry/OC mild pairing.]