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
Find all Figments
Return to where it all started
Crack all Vaults
Tag all Emotional Baggage
Achieve Rank 100
Break all 3 Gramaphones in Fatherland Follies
Scavenge all MISSION CRITICAL PSYCHONAUTS ASSETS
Dissolve the Deluge of Grulovia
Purchase all Pins
Frequent Fatherland Follies
Completely fill your Astral Wallet
Soothe Lucrecia's Lament
Take a photo with the Otto Shot
Peruse Cassie's Collection
Empty Bob's Bottles
Discover the Astralathe
Raid the Tomb of the Sharkophagus
Treat Ford's Follicles
Repair Ford Fractured
Recover your mental energy with a Dream Fluff
Complete Gisu's Psychoseismometer Quest
Complete Queepie Quest
Complete Lili's Request
Purchase all Otto Shot Filters
Max out your PSI Pop capacity
Max out your Dream Fluff capacity
Help Dion Setup Aquatodome
Deliver Cruller's Correspondence
Achieve Rank 50
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 Regret's anvil at another enemy
Throw a Judge's gavel back at him
Upgrade to the Astral Wallet
Fully upgrade a Badge
Find the Family Camp
Pyro 3 enemies 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
Consume a PSI Pop to restore some mental energy
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
TK throw an object to stun an enemy