If the scar was a horcrux, and you hit it with the curse, maybe it would work...
I had an idea before that since the two of them were linked, then Harry would die with Voldemort, but like Buffy, one of his friends revives him. (I'm talking about Season 1 when Xander gives her mouth to mouth. She was dead for a minute and came back.) Or that Harry does not use his wand to defeat Voldemort; instead he pushes him into the Veil. Personally, I like that idea. I envisioned both of them falling into the Veil, locked in combat, and then, because he's Harry and weird stuff always happens, he unexpectedly emerges from the Veil. Stranger things have happened.

You should see all of the fanfiction I've written about possible endings to the series. Boggles the mind.