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