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