I would find Stephanie Meyer, as she was setting the last paragraph of the first 'Twilight' book to paper in the dark of the night. I would move silently through her house, completely unknown beneath the sound of her ticking clock and tapping keyboard as she finalized those hellishly disjointed words upon the page.
I would muffle her mouth and pull back her head, and whisper a sickly sweet song of death and damnation in to her ear. And then, with a dagger consecrated in mead, flame, and desperation during the Winternacht
blót, I would strike Seven Blows for Justice, Seven Blows for Freedom. Seven Blows for Love, of an art now twisted in to something wicked. The dagger will cry out with each vengeful thrust, Seven horid screams not of this hallowed Earth. Any mortal who hears it shall
always hear it, and will know what has happened; but they will never speak of it, for fear that the screams will one day be for them.
And then, I would open
Angayar-Degalal's Bottle of Dusky Mists, an artifact long forgotten and retrieved from a forbidden place, at a cost that I can not discuss. The bottle will consume her soul, dooming it to float in the sickly sweet ether of the Bottle's own pocket dimension. It will be forever caressed by hands not quite warm, but not quite cold; almost so soft as to be sticky, and just visible enough to be seen from the corner of an eye. Her being will be picked apart over and over, more times than can be counted, and scrutinized upon the dinner table of Eternity itself.
I would leave as silently as I came, after 'discovering' a fault in the electrical system of her home,
to Cleanse that spot of earth in flame.
The world may end and the sun may envelope the inner planets. The Universe may reverse creation and collapse in on itself. The Bottle has seen these things more times than they have actually happened, yet never once come out worse for the wear. When Thor is slain and Odin has fallen, and Surtr's sword rips fire through the sky, the Bottle shall endure; and so for all time (and yet, for NO time, as the bottle is timeless), Ms. Meyer will always know exactly how I feel about her.
Anyway, yeah, that's what I'd do if I could change just one thing. Maybe. I might have a different idea tomorrow and ask for a do-over. Maybe I'd buy more lotto tickets or something.