Alone in the Dark: Illumination

Technically speaking, there are only 2 ways to obtain this achievement in a legit way: either you preordered the game, or you've beaten all 3 campaigns on Hard.
The first way works, the other doesn't. It's not the first thing broken in this game and it certainly ain't the last.

So how can you actually get the achievement if you didn't preorder the game? Easy: family sharing.
Find someone who preordered the game and ask him/her to share his/her library with you (make sure he/she has the Eldritch edition DLC, that's the preorder bonus).
If you don't have the game, you have no additional steps. Just launch the game and you're good to go.
If you do happen to have the game, you'll have to delete the game through Steam support first and restart Steam (just to be sure) before you'll be able to get the achievement. Once it's done, launch the game, get your cheevo then restore the game through Steam support (that's how I did it).