Just finished the game, have all achievements except for 3, ultra hard completed, new game+ completed, all achievement obtained, and one that is marked as a secret (marked as rare with 6.2% currently having obtained it).

I've looked through all the online guides, mainly for PS or Steam, and it seems like GoG has one extra achievement. Anyone know what it is, or where I can see the entire GoG list?

Nevermind - after going through the lists a third time (would help if I could sort the list in GoG Galaxy) finally found the one I was skipping over, clearing all corrupted zones. Easy enough if I decide to try to complete them all.

GG, I can't wait to play this just have to finish some other games to make room on hard drive.