Here is the full list of all 57 Psychonauts 2 achievements. It takes around 25-30 hours to unlock all of the achievements on Windows.
Recover your mental energy with a Dream Fluff
Return to where it all started
Take a photo with the Otto Shot
Max out your Dream Fluff capacity
Max out your PSI Pop capacity
Purchase all Otto Shot Filters
Purchase all Pins
Acquire all Upgrades
Find all Figments
Achieve Rank 100
Tag all Emotional Baggage
Crack all Vaults
Break all 3 Gramaphones in Fatherland Follies
Completely fill your Astral Wallet
Revisit a brain through the Collective Unconscious
Complete Lili's Request
Scavenge all MISSION CRITICAL PSYCHONAUTS ASSETS
Complete Gisu's Psychoseismometer Quest
Complete Queepie Quest
Upgrade to the Astral Wallet
Dissolve the Deluge of Grulovia
Frequent Fatherland Follies
Soothe Lucrecia's Lament
Peruse Cassie's Collection
Achieve Rank 50
Empty Bob's Bottles
Discover the Astralathe
Raid the Tomb of the Sharkophagus
Repair Ford Fractured
Treat Ford's Follicles
Pyro 3 enemies at once
Deliver Cruller's Correspondence
Complete PSI King's Sensorium
Find the real Panic Attack during his Phantom attack
Tune in to a Stray Thought
Equip 3 Pins at once
Bowl Strike City
Plate Compton's Cookoff
Throw a Judge's gavel back at him
Help Dion Setup Aquatodome
Find the Family Camp
Visit the Collective Unconscious
Cool Hollis' Hot Streak
Shut Down the Luctopus
Consume a PSI Pop to restore some mental energy
Fully upgrade a Badge
Make a connection in Hollis' Classroom
Achieve Rank 10
Upgrade your first Badge
Receive your first assignment
Talk to Milla in her Office
Equip your first Pin
Combine PSI Cards with a PSI Core at the Otto-Matic
Achieve Rank 2
Navigate Loboto's Labyrinth
Throw a Regret's anvil at another enemy
TK throw an object to stun an enemy