Here is the full list of all 30 Downward achievements.
Perform 500 wall-jumps.
Perform 500 double jumps.
Get a Gold medal in the Challenges.
Buy all the upgrades of the Old Man's Room.
Obtain 2000 Skypieces.
Unlock all Meditation skills.
Obtain 1000 Skypieces.
Unlock all Wisdom skills.
Build four different rooms in the Merchant's Lair.
Sell 15 items to the Merchant.
Unlock all Pursuance skills.
Sell 5 items to the Merchant.
Unlock all Insight skills.
Unlock all Endurance skills.
Obtain 500 Skypieces.
Gather 50 Dry Artifacts.
Obtain the Slingshot Artifact.
Gather 25 Dry Artifacts.
Reach the temple on top of the cliff.
Die from a Drone explosion.
Obtain the Double Jump Artifact.
Exit the tutorial area.
Defeat your first golem.
Use the Mark for the first time.
Wake Up!
Get 10 Gold medals in the Challenges.
Perform 500 wall-runs.
Perform 500 slingshots.
Survive your own recklessness.
Die from a Cactus.