First, Jinx all Voldemort's skeletons. He will cast Abvra Cadabvra and you must move the energy ball over the skeletons. He will then pick up the grim reaper statue and make it float around. Dodge it and on about the third time it is thrown at you, it will get stuck in the ground. Move the energy ball over it, and it will lose a wing. Do this two more times and you will win.