There is a glitch for this achievement where if you complete the game on Ranger Hardcore it becomes impossible to unlock on your next playthrough.
The issue is that Ranger Hardcore difficulty gifts you all of the suit upgrades from the get-go, and the game is designed so that if you pick up a collectible it's removed from the game entirely (same as postcards and notes).
The act of picking up a suit upgrade is what gives you credit towards your achievement progress, and since the physical upgrades are removed from the game environment, you're stuck.
So basically this is a warning, make sure you get this BEFORE you attempt Ranger Hardcore difficulty.