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