Quote Originally Posted by Alphys View Post
Yeah I won't spoil the effects just yet then.

Yeah the genocide run lets on arguably more about the story than pacifist does.
So...

Spoiler:
I know about what happens if you select "Do not" when Chara prompts you to erase the world (I couldn't help watch the collection of YouTubers reacting to the jumpscare. It was pretty funny.). But everything between the Sans battle and that, I haven't really seen. I just know Asgore and Flowey get axed but that's about it.