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