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