Here is the full list of all 123 Cassette Beasts achievements.
Come face-to-face with a faceless being.
Defeat an ancient force brought back to full strength.
Overcome the essence of fusion.
Obtain a Poison-type bootleg
Get to 5 hearts with Eugene
Get to 5 hearts with Felix
Prove your worth to a certain warrior.
Get to 5 hearts with Meredith
Obtain 120 different species
Defeat 50 Rogue Fusions
Obtain an Earth-type bootleg
Obtain a Plastic-type bootleg
Defeat an Unstable Fusion
Complete 5 noticeboard quests
Try to sneak past a battler by jumping over their head
Obtain a Lightning-type bootleg
Obtain a Metal-type bootleg
Open a door long since thought lost.
Defy all odds in a place between worlds.
Obtain a Fire-type bootleg
Obtain the Averevoir Flight ability
Obtain 100 different species
Defeat 20 Rogue Fusions
Solve the riddle of Morgante's song.
Reopen every station
Observe 120 different species
Win a battle before it starts
Get the Fusion Radar
Defeat Ianthe and become a Ranger Captain
Help Sunny start a new life
Complete Eugene's quest
Defeat Babelith
Complete Morgante's song
Defeat a ghost
Defeat Alice
Enter a romantic relationship
Meet the Travelling Merchant
Defeat 10 Rogue Fusions
Obtain Candevil
Help Hoylake with his research
Defeat Lamento Mori
Defeat Captain Codey
Defeat Captain Heather
Visit every part of New Wirral
Defeat Heckahedron
Defeat Captain Gladiola
Get to 5 hearts with Kayleigh
Clear 5 Landkeeper offices
Obtain a Glass-type bootleg
Complete Barkley's quest
Unlock Barkley
Obtain the Pumpkin Vine Ball ability
Find a helping hand in a place far away.
Find yourself somewhere far away.
Obtain 50 different species
Complete Viola's quest
Bring Viola to the shipwreck
Defeat Captain Cybil
Unlock Viola
Defeat Captain Buffy
Defeat Captain Lodestein
Defeat Captain Wallace
Defeat Captain Zedd
Complete Felix's quest
Meet Kuneko at 4 altars
Meet Kuneko at 3 altars
Meet Kuneko at 2 altars
Defeat 5 Rogue Fusions
Meet Kuneko at 1 altar
Meet Kuneko
Clear 4 Landkeeper offices
Obtain a rare sticker
Clear 3 Landkeeper offices
Complete Meredith's quest
Bring Meredith to the mall
Unlock Meredith
Defeat Captain Clee-O
Defeat a Swarm
Defeat Captain Skip
Obtain 20 different species
Obtain the Electromagnetism ability
Defeat Captain Judas
Clear 2 Landkeeper offices
Complete Kayleigh's quest
Unlock Felix
Obtain the Diveal Swim ability
Defeat Captain Penny Dreadful
Choose a design for Harbourtown's sign
Obtain 10 different species
Obtain an Ice-type bootleg
Remaster a tape
Start Kayleigh's quest
Obtain the Bulletino Dash ability
Defeat Poppetox
Investigate a rumour
Meet the one who dutily attends the stations.
Sign up to the Rangers
Defeat a Rogue Fusion
Obtain a rumour
Clear 1 Landkeeper office
Unlock Eugene
Complete the tutorial
Obtain the Mothwing Glide ability
Unlock Kayleigh
Obtain Bansheep
Defeat an Orb Fusion
Obtain additional data on every species
Obtain a Beast-type bootleg
Obtain a Plant-type bootleg
Obtain a Water-type bootleg
Obtain an Astral-type bootleg
Obtain an Air-type bootleg
Obtain a Glitter-type bootleg
Obtain a monster form thought impossible to find.
Get to 5 hearts with Barkley
Get to 5 hearts with Viola
Complete Frankie's training
Complete Vin's training
Complete 20 noticeboard quests
Complete 50 noticeboard quests
Complete 100 noticeboard quests
Win a battle while ghostly
Win a battle while Gambit is active