I don't own anything from the Harry Potter universe, but JK Rowling does. I hope this wouldn't offend her too much! I wrote this ages ago, when book 7 was nothing but a blot on a distant horizon. Perhaps it should be considered an alternate ending to the series?
Harry Potter and the Fateful Curse
Harry crept down the dark corridor, the hand clutching his wand trembling slightly and making the small light he'd conjured at the tip of it blink for a moment.
This is it, he thought, this is the moment the whole wizarding world's been waiting for.
He knew where Voldemort was hiding; he knew that the potion Snape had prepared and ensured the Dark Lord took would be working by now. You-Know-Who had been weakened; although he had not lost his powers entirely, they had been reduced sufficiently to ensure that when Harry finally reached his destination and was able to deliver the killing curse, it would not fail.
Finally Harry pushed through the heavy wooden door and entered the Dark Lord's private chambers, hidden deep underground in the desolate wasteland surrounding Malfoy Manor. Draco Malfoy, realising just too late into the final battle exactly which side he should have been fighting for, had used his final breath to reveal the destination to Hermione Granger, who had been cradling the dying boy's head in her lap in an effort to bring him some comfort. The last words he'd heard were her whispered "thank you", and the blond had died with a small smile on his lips.
The Boy-Who-Lived readied himself as the sound of the door slamming back into place alerted his target to his presence. Lord Voldemort's head turned towards him, and the slow speed at which the action occurred made Harry's heart leap joyfully in his chest. The potion had worked! Not that he had doubted where Snape's true loyalty laid, not really, but to see the evidence with his own eyes was wonderful.
Harry raised his wand and began to say the words which would end it all.
"Ava-"
Red eyes burned into his face as if Voldemort was looking past his physical presence at his very soul. Harry faltered.
"Avada Ked-" he tried again only to break off with a whimper. Those eyes...the pain...
Come on Harry, you can do it! He could hear Ron willing him on in his head, and he saw again before his eyes the crumpled body of his best friend as it had laid at the very edge of the Quidditch pitch, the scene of the final battle. The red hair had stood out starkly against the whiteness of Ron's rapidly cooling skin, the freckles seeming to fade as Harry watched, and that memory alone was enough to stiffen the young wizard's resolve. Do it for Ron.
His scar hurt unbearably now and he could hardly think of the words he needed, let alone say them. He made one final effort to concentrate his mind and then strode forward, his wand pointing directly at Voldemort's heart. This was the end; after this it would all be over.
Harry's voice was strong and confident as he flung the words of the curse towards the Dark Lord.
"Abra-Cadabra!"
Oh, bugger.