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