So, my first nitpick about the original story is this: Why would Chara reset and redo the Genocide run hundreds of times? They're rather clearly confused with (and likely uninterested in) the action of recreating the destroyed world just to erase it again. They go to as far as state that the player is "wracked with a perverted sentimentality" if they do this. I think that Chara's goal in the Genocide route, the goal that they feel they were revived to achieve, was to reach the absolute (which I think refers to reaching the maximum level of strength in the game), and do away with the world when the deed was done. So, why would they bring a "pointless" world back, just to go back to square one and reach the absolute all over again?

Another nitpick I have is that, well, I feel like it would make more sense for someone like Flowey to go on a Geno run to counteract the player's own attempt. Going out of your way to kill everyone you can possibly find, even if it's to try and counter some bigger threat, requires a concerning lack of qualms regarding the morality of it all, and I feel like Flowey, one who has happily desensitized himself to killing all sorts of people when he could still save, load, and reset his progress, would be a lot more willing to kill everyone to fight back against you than Sans. I also think that him managing to remember the constant Geno runs, bypassing whatever complete reset Chara pulls of at the end of one, is more plausible than Sans doing the same, if only because he's done so before with normal resets.

So, uh, yeah, in other words, funni kill-y flower boy would be much better and dusting than punni sad skull man