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