Board Thread:Questions and Answers/@comment-31440537-20170324205915/@comment-27701762-20170324212302

You can manually edit the number of kills you have by editing the "Kills" value in the undertale.ini file, along with the corresponding number in "file0" and "file9" (these should be the 12th line in the file, or the 11th line after the name line).

I don't recall if this works for being able to get the True Pacifist ending, though I think it does, though there might be other issues if you killed any story characters.

It doesn't appear to work if you're trying to skip the grinding for the Genocide Route.