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