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
Complete Gisu's Psychoseismometer Quest
Achieve Rank 100
Purchase all Otto Shot Filters
Scavenge all MISSION CRITICAL PSYCHONAUTS ASSETS
Purchase all Pins
Recover your mental energy with a Dream Fluff
Return to where it all started
Complete Lili's Request
Max out your Dream Fluff capacity
Max out your PSI Pop capacity
Completely fill your Astral Wallet
Find all Figments
Tag all Emotional Baggage
Break all 3 Gramaphones in Fatherland Follies
Crack all Vaults
Throw a Judge's gavel back at him
Throw a Regret's anvil at another enemy
Complete Queepie Quest
Dissolve the Deluge of Grulovia
Frequent Fatherland Follies
Soothe Lucrecia's Lament
Revisit a brain through the Collective Unconscious
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
Bowl Strike City
Achieve Rank 50
Equip 3 Pins at once
Plate Compton's Cookoff
Help Dion Setup Aquatodome
Find the Family Camp
Deliver Cruller's Correspondence
Complete PSI King's Sensorium
Find the real Panic Attack during his Phantom attack
Tune in to a Stray Thought
Take a photo with the Otto Shot
Fully upgrade a Badge
Treat Ford's Follicles
Upgrade to the Astral Wallet
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
TK throw an object to stun an enemy
Achieve Rank 10
Receive your first assignment
Upgrade your first Badge
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