Here is the full list of all 21 Tchia achievements.
Discover all the Campfires
Discover all the Docks
Upgrade your Stamina to 120
Upgrade your Soul-Meter to 10 slots
Wear the Umbrella Hat
Wear the complete Pirate outfit and boat style
Wear the complete Crab outfit
Win something in a Claw Machine
Score 100% in any Music Sequence
Shoot down a flying bird with the Slingshot
Burn 3 enemies at once with a single object or explosion
Soul-Jump into an object right after Soul-Throwing it
Reach the Endgame
Find and Soul-Jump into Pwi Dua's hand
Find and open all the Treasure Chests
Unlock every cosmetic items for Tchia and Boat
Unlock every Soul-Melody
Clear all the Soldier Camps
Destroy every Meavora Statue
Shout from every Point Of View
Reach 100% Game Completion