Shakugan no Shana S03 E10 Crossing

Sophie Sawallisch comes to assist with a large army of armed humans. Shana breaks free and after a battle against a Denizen, which ends up with Shana furiously killing it, she comes to self-awareness as the ultimate combination of the Flame-Haired Burning-Eyed Hunter - the Flame Haze, and Shana - the human she became after meeting Yuji.