Complete three Hidden-Object Puzzles without using the Hint button.*MISSABLE*
As the description says, you need to complete any three HOPs in the game without pressing to use a hint. There are close to 10 HOPs in the game, and this is the only one that requires you to not use hints. Assuming you're playing on Casual difficulty, you can mash through all HOPs to find all of the objects with relative ease.
Once you unlock this achievement, feel free to use hints during HOPs as much as you want to speed them up on top of mashing through them.