Disclaimer: I do not own the Harry Potter or Avatar universes, or anything therein that is the author's original work. I do, however, own any unique creations that do not fall into the original universes and that I may claim as my own intellectual property.
Harry Potter looked at the carnage surrounding him with shocked stoicism. The rain was coming down hard now, washing the gently rolling mud hill of its contaminants, the uprooted grass which had been used as knives and needles, swirling around by magically created tornados, now being washed down the muddy slopes into the valleys and creeks. The hill was once grassy, but the constant spellfire, infernos, and transfigurations had taken its toll on the landscape, turning a once ideal setting into a warzone. Now the blades of grass were discarded, left to die after they had been yanked from their roots for a single moment of glory, to cut flesh or block curses or blind the enemy; laying more numerous than the hundreds of human corpses besides. The grass was dead too, little green corpses first used to kill, then to trample upon, then finally used as a deathbed. The rain was coming down hard, cleansing the mud of the grass bodies, and cleansing it of the blood.
Before Harry was a pile of ashes in the shape of a human, like the chalk outline of a New York slums sidewalk, resisting the hard rain's cleansing effort. Voldemort left no body to remember or to bury, just ash, a reminder to Harry of what Voldemort wanted of the world. Complete conquest had been Voldemort's goal, and if he had to reduce the world to flames, then Voldemort would be happy ruling from a throne made of ash.
And that's exactly what he had done. Off in the distance was London, still burning from the Hellfire that his Death Eaters had summoned. Around Harry lay the bodies of his friends– Ron, Hermione, Ginny, the Weasleys– all given to place Harry close to Voldemort, to give him the opportunity to inflict the power that the Dark Lord new not. Who would have guessed that the power that Voldemort knew not was vengeance? Love had not killed Voldemort. Harry did not feel sorrow or compassion as he delivered the fatal blow– not when the bodies of everyone he loved surrounded him. What Harry felt was rage and hate, both of which came together to form the power that Voldemort never expected. He was dead, but he still set the world on fire. He had won after all. Here on this hillcrest Voldemort could see his conquests burning, see Harry's friends dead and gone, and smile upon his victory. Here Voldemort would forever stay, sitting and laughing on his throne of ashes.
Harry's wand had burnt to charcoal as he cast the killing blow. It hadn't been a spell that had killed Voldemort, and the incantation was nothing more than an animalistic scream, but the force was strong enough to destroy Harry's wand and burn his hand. Harry could smell his own flesh burning, and the wand was still too hot. The tip was glowing like a match head, embers still hissing and releasing a trail of smoke against the fat raindrops.
Feeling returned to his hand with sharp intensity and Harry dropped his wand with a cry. At first it stuck stubbornly to his blistered sticky skin, but then it fell down and into the ashes of Voldemort. The ashes roared to life with green flame, identical to those Harry had seen numerous times in the fireplaces throughout the wizarding world. He stepped back in surprise, his eyes widening before he quickly remembered the despair he was supposed be feeling. The amazement faded, and he looked at the corpse-Floo with a new apathy. The green fires raged up before him still strong, and Harry turned from them, his soiled and soaked trainers squelching in the deep mud.
He turned, and saw Hermione's body there next to him. She had been the last to fall, protecting him from the worst of Voldemort's attacks. But she had protected him by taking the attacks herself. Her eyes were open, her face contorted in pain, and her body had been broken. He looked into Hermione's face and stumbled away in fear. She couldn't be dead! They couldn't all be dead! He was alone now, the last one to realize the great nothingness of the universe, and the last one to care about it. The others were beyond caring. Harry fell into the mud, away from Hermione. He kicked his heels, cutting channels into the ground with trainers that filled with rainwater and scooped up goopy mud with his hands. He scuttled backwards like a worm and into the green flames.
The graveyard hillside disappeared in an explosion of grey and red, and Harry knew that he was being taken away by something similar to a Floo or a Portkey, perhaps a mixture of both, but could not bring himself to care. Be it a final trap from Voldemort or a laughable reward from providence, Harry closed his eyes and waited for the journey to end. There were no tears shed, for he had no emotion left to create them. He was consumed by an apathy and emptiness so vast that the closed his eyes, unwilling to expend the effort to identify and interpret the hue of the colors that raged around him. Harry had done his job, and there was nothing left to do but wait until he too didn't care about how empty the universe really was.
The journey lasted longer than Harry had expected.