Here is the full list of all 35 Mutiny!! achievements.
Witness the Mutiny ending for Alcina
Complete all of the Core Game Achievements
Witness the Mutiny ending for Elizabeth
Witness the Mutiny ending for Grozdana
Witness the Mutiny ending for Lara & Lirdynrae
Witness the Mutiny ending for Nemui
Witness the Normal ending for Alcina
Witness the Normal ending for Elizabeth
Witness the Normal ending for Grozdana
Witness the Normal ending for Nemui
Witness the Happy ending for Elizabeth
Select Elizabeth as your first mate
Witness the Happy ending for Grozdana
Select Grozdana as your first mate
Witness the Happy ending for Lara & Lirdynrae
Select Lara and Lirdynrae as your first mates
Witness the Happy ending for Alcina
Complete the last Ship Fight
Select Alcina as your first mate
Witness the Happy ending for Nemui
Complete 'The Hole' chapter of the story
Complete 'The Underwater Garden' chapter of the story successfully
Complete 'The Mansion' chapter of the story successfully
Complete the Runes puzzle
Complete 'The Break At The Port' chapter of the story
Complete 'The Biome Ruins' chapter of the story successfully
Complete 'The Snowy Ruins' chapter of the story successfully
Impress the Creditor
Complete 'The Mountain Dungeon' chapter of the story successfully
Select Nemui as your first mate
Complete 'The Undersea Ruins' chapter of the story
Complete 'The Underwater Ruins' chapter of the story
Complete 'The Cloud Ruins' chapter of the story successfully
Complete the Lights On puzzle
Become captain of your own ship