LogFAQs > #986153381

There's some little interesting stuff were you to reload after. Instead of the select menu, there's just a blank void with the sound of howling wind playing. If you let it sit for a long time, eventually Chara starts speaking to you again. They deny you the ability to reset the game anymore. They offer to restore the world if you agree to trade your soul to them. This causes a full reset of the game, except the pacifist endings become permanently altered.

If you do that and then finish genocide AGAIN, then Chara says one of my favorite lines in the game: "You are wracked with a perverted sentimentality."