So today (03/10/2018), I pushed an update to Underlauncher, with the new version now being 22.214.171.124. There wasn’t a huge amount at all included in this update but I’ve changed a bit of logic around in regards to adding and removing the effects of the Genocide Run which is now a lot better for Steam users.
tl;dr when I deleted the files in the game’s save directory which indicated that a Genocide run had been completed, Steam Cloud save auto restored them making the functionality very inconsistent.
To fix it, as per what I myself and other users do to get around the issue, I decided to write the Genocide files to the directory in any case, but if we’re disabling the effects, I set the read permissions of the file to be denied. That way, Steam won’t auto restore the file as it still exists, but the game is unable to read the file so it THINKS it doesn’t exist which is ideal.
So yeah, if anyone has any further feature suggestions/bug reports, shoot me an email at email@example.com.