Overview
When you complete the Genocide route (spoilers) your game will be fully destroyed. So if you’re feeling up to reset your game without selling your SOUL then here is a guide that will show you how.
First Part
1: Exit Steam. (Make sure it is completely closed)
2: Go to Computer > Local Disk (C:) > Program Files (x86) > Steam > userdata > (Folder of you Steam Id) > 391540 > remote > system_information_962 or system_information_963 .
3: Open the file in Notepad and delete everything in there (so the “a”) and save.
4: Now close the file and back out from the remote folder into the 391540 folder.
5: Delete remotecache.vdf .
6: Start up Steam then Undertale and you will get a Cloud Sync Conflict window.
7: While the Cloud Sync Conflict window is open, remove everything in the 391540 folder.
8: Click on ‘Upload to the Steam Cloud’ on the Cloud Sync Conflict window.
9: Start up Undertale and while it’s running, right click on Undertale in the Steam window and click on Properties.
10: Go to the Updates tab and disable Steam Cloud synchronization.
11: Exit Steam and Undertale.
12: Back out to your Steam Id folder and delete the 391540 folder.
Second Part
1: Open up the Start Menu and search for ‘run’ (the program).
2: Type in %appdata% .
3: Back out into the AppData folder and open up the Local folder.
4: Open up the UNDERTALE folder and delete system_information_962 or 963
The End
I hope this helped you reseting the game. If there are still some problems then just write it in the comments bellow. And also check out my other guide:
[link]