Here is the full list of all 39 Rainbow Billy: The Curse of the Leviathan achievements.
Break the Curse of the Leviathan and save the World.
Raise ALL creatures' friendships to Level 3!
Raise 40 creatures' friendships to Level 3!
Raise 30 creatures' friendships to Level 2!
Catch at least one of each kind of fish!
Hear each and every one of the The Confessor's secrets.
Befriend all creatures.
Climb to the highest point in each area of the World.
Discover Disco Broccoli!
Peek through the window...
Accept your other self and befriend Shadow Billy.
Get reprimanded for punching barrel-kind.
Raise 20 creatures' friendships to Level 3!
Collect ALL Thought Upgrades!
Collect 75 Thoughts.
Glide using the Billy-Copter for more than 5 straight seconds!
Fast travel between two distant areas of the World.
Face your fears and befriend Calypso.
Talk to all Kickstarter Backers characters!
Collect 50 Thoughts.
Discover the broken warp pipe.
Own 500 coins or more.
Collect 25 Thoughts.
Fight toxic masculinity and befriend Dragalant.
Flawlessly complete a difficult "Dodge" attack minigame!
Flawlessly complete 50 attack minigames!
Dig up 15 buried treasures.
Raise 5 creatures' friendships to Level 2!
Flawlessly complete a difficult "Circle" attack minigame!
Flawlessly complete a difficult "Slots" attack minigame!
Flawlessly complete a difficult "Paddle" attack minigame!
Catch 10 non-gummi items while fishing.
Collect 10 Thoughts.
Recolor five colors in one blow!
Catch three different objects in one fishing session!
Flawlessly complete a difficult "Line" attack minigame!
Destroy 25 Objects!
Convert a Thought into a Figment of Imagination!Service.
Listen to Friend-Ship whistle for more than 5 straight seconds.