Ori and the Blind Forest: Definitive Edition - Nintendo Switch

Just clearing some things up, here:

You CAN do this on the easiest difficulty. The 'Easy' difficulty makes you receive less damage and deal more damage across the board, so it helps to set it to 'Easy' at the beginning of the game to get through certain encounters faster.

There is PLENTY of room for error. I once died in my run and was sent back to a checkpoint I made 2 minutes ago, and I ended the game with more than 30 minutes to spare. As long as you aren't wandering way off course or taking massive detours to snag collectibles, you should be fine.

I recommend you only grab collectibles you cross paths with on your way through the main story. For example, in the room near the beginning of the game where you need to use light burst to release the spider-web-sack from the ceiling, there is a life cell in the upper-right-hand side that you can grab in around 10 seconds or less. Those are the collectibles I'm referring to. In the end I only found 2 life cells and 5 energy cells, but that couldn't stop me from beating the game fast enough to get the achievement.

Be sure to use teleporters whenever you can, it speeds things up considerably. For example, once you exit the Ginso Tree, find the nearest teleporter and warp yourself to the spot where the Spirit Tree is visible in the background. This puts you almost on top of the next story segment. I'm fairly certain you couldn't teleport in vanilla Ori(which also had this achievement), so taking advantage of this ability turns this achievement into a cake walk.

I hope this helped in some way, happy hunting!