AN: I don't own any part of Harry Potter and never will.
The Last Battle
The last battle is taking place and it is being fought at Hogwarts. The Order of the Phoenix members and the Death Eaters are locked in many little one-on-one scuffles. There are curses bouncing everywhere, colliding with each other, taking chunks of dirt out of the ground, destroying trees all over the place.
Harry and Voldemort are in a battle of their own. There are no other battles within a hundred metres of them. Their battle is so heated that all you could see if you were watching on are two blurs and many different colour lights. The battle may be heated but Harry and Voldemort are roughly ten metres apart.
Harry has Voldemort on the ropes; sending spell after spell at Voldemort. Voldemort's backing back at the ferocity of Harry's attacks. As they move a path of destruction is left behind them.
As Voldemort is concentrating on Harry's attacks he doesn't realize their position in the grounds. Just after Voldemort deflects an Impedimenta charm he is hit by a huge branch that sends him flying five metres. Quickly he is on his feet but then has to dodge Harry's spells and the Whomping Willow's branches; both of these things giving him no time to cast any spells.
After about five minutes of this Voldemort finally sees an opening and takes it, the whole Whomping Willow seemed to bend away from him. Voldemort just managed to fire off one killing curse before every branch of the Whomping Willow came down of top of him, crushing him to death.
Harry dodged the killing curse and, after checking that the lump of blood and flesh that was Voldemort was really dead and picking up Voldemort's, strangely, unbroken wand, ran off to join the other fights around Hogwarts.
This is how Voldemort died not the way most people would think but it is the way it happened.