Here is the full list of all 39 The Medium achievements.
Find all Echoes in a single playthrough.
Find all of Thomas' notes in a single playthrough.
Find all of Frank's postcards in a single playthrough.
Escape the creature without alerting it.
Finish the game.
Complete the broken mirror.
Make it through the pump station.
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.
Send the Childeater away.
Experience your first vision of Thomas.
Find all pages from Richard's diary in a single playthrough.
Acquire the bolt cutters.
Use a mirror to cross over.
Survive a monstrous encounter.
Inspect 100 objects in a single playthrough.
Find a note from a troubled man.
Spend 10 minutes outside your body.
Burn through the moths using Spirit Shield.
Acquire the razor.
Find a page from a mentor's diary.
Reconstruct a Memory Shard.
Meet Sadness.
Inspect 50 objects in a single playthrough.
Run 2 kilometers.
Use Insight for at least 15 minutes.
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.