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.
Complete all cairns.
Activate all frescos.
Read all of Bianca's journal entries.
Listen to all shells.
Turn all altars.
Use the echo on a frozen ballast in Chapter 6.
Place a piton at the top of a wall run.
Stop 25 pebbles with a single echo from the ballast.
Hug the ballast 20 times.
Complete the game.
Restore your stamina more than 50 times while climbing.
Warm up the ballast in chapter 6.
Complete more than 200 jumps or double jumps in one game.
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.