Here is the full list of all 21 Jusant achievements. It takes around 5-6 hours to unlock all of the achievements on Windows.
Read all letters.
Read all of Bianca's journal entries.
Turn all altars.
Listen to all shells.
Complete all cairns.
Activate all frescos.
Complete the game.
Use the echo on a frozen ballast in Chapter 6.
Warm up the ballast in chapter 6.
Hug the ballast 20 times.
Stop 25 pebbles with a single echo from the ballast.
Complete more than 200 jumps or double jumps in one game.
Restore your stamina more than 50 times while climbing.
Place a piton at the top of a wall run.
Turn an altar.
Scare more than 10 chocos back to their burrow.
Hug the ballast.
Activate a fresco.
Complete a cairn.
Listen to a shell.
Read a letter.