Here is the full list of all 39 The Medium achievements.
Escape the creature without alerting it.
Find all pages from Richard's diary in a single playthrough.
Finish the game.
Complete the broken mirror.
Find all of Thomas' notes in a single playthrough.
Make it through the pump station.
Find all Echoes in a single playthrough.
Uncover the mystery of the burned down house
Find the Red House.
Send the Hound away.
Experience your second vision of Thomas.
Reconstruct all Memory Shards in a single playthrough.
Find all of Henry's Echoes in a single playthrough.
Defeat the creature in the flooded ruins.
Find all of Frank's postcards in a single playthrough.
Send the Childeater away.
Experience your first vision of Thomas.
Acquire the bolt cutters.
Use Insight for at least 15 minutes.
Use a mirror to cross over.
Survive a monstrous encounter.
Inspect 100 objects in a single playthrough.
Spend 10 minutes outside your body.
Find a note from a troubled man.
Burn through the moths using Spirit Shield.
Acquire the razor.
Find a page from a mentor's diary.
Reconstruct a Memory Shard.
Run 2 kilometers.
Meet Sadness.
Inspect 50 objects in a single playthrough.
Find an Echo of a mysterious caller.
Find an Echo.
Reach the hotel.
Use Spirit Blast to create electricity.
Find a postcard from the groundskeeper.
Send Jack's spirit away.
Inspect 25 objects in a single playthrough.
Feed the cat in Jack's apartment.