Here is the full list of all 20 The MISSING: JJ Macfield and the Island of Memories achievements.
Escape from something scary.
Jump over that black thing!
Read all of F.K.'s hidden texts after finishing the game.
Read all of the texts from the past.
Select Continue after the ending and start a new run.
Read a hidden text from F.K. after finishing the game.
Complete the game.
Reach the top of the clock tower.
Acquire every donut.
Escape danger.
Find every Sleepy.
Don't get too addicted to your phone.
Fall off a bridge.
Get run over by a train.
Crane operation is dangerous work.
Find the first Sleepy.
Chat with F.K. for the first time.
Let the strange deer empower you.
First, you need to find Emily.
Awaken at the campground.