User blog comment:Smartboy201/Destroying Biohazard Piles-Glitch (Spoilers for The Last Agent DLC)/@comment-4694083-20150221105336/@comment-1494687-20150222182249

There seems to be a thing in which people state that, before doing this, to be sure to back up your data on Steam, first, then delete it, disconnect from "the cloud", then complete the achievement, then replace the data with the backup data... or something.

That's for Steam on PC, though. It seems that the XBOX-version actually has over ten steps, to fix it. I mean, at least the PC-version gets by with a lot less, but... deleting the main game-data JUST to get this? Nnngh... I wanted to honestly do the co-op achievement LAST, but ended up doing it a couple of days ago, since I do NOT trust myself with backing up data properly, without a tutorial on where everything's going, what to do with it, and when to do it... *shudders*