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