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