Here is the full list of all 39 Rainbow Billy: The Curse of the Leviathan achievements worth 1,000 gamerscore.
Own 500 coins or more at one time
Befriend all creatures.
Raise 30 creatures' friendships to Level 2!
Raise 5 creatures' friendships to Level 2!
Raise 20 creatures' friendships to Level 3!
Raise 40 creatures' friendships to Level 3!
Raise ALL creatures' friendships to Level 2!
Dig up 15 buried treasures.
Catch three different objects in one fishing session!
Catch at least one of each kind of fish!
Catch 10 non-gummi items while fishing.
Listen to Friend-Ship whistle for more than 5 straight seconds.
Fast travel between two distant areas of the World.
Get reprimanded for punching barrel-kind.
Glide using the Billy-Copter for more than 5 straight seconds!
Face your fears and befriend Calypso.
Discover Disco Broccoli!
Fight toxic masculinity and befriend Dragalant.
Hear each and every one of the The Confessor's secrets.
Talk to all Kickstarter Backers characters!
Break the Curse of the Leviathan and save the World.
Accept your other self and befriend Shadow Billy.
Climb to the highest point in each area of the World.
Discover the broken warp pipe.
Peek through the window...
Destroy 25 Objects!
Flawlessly complete 50 attack minigames!
Flawlessly complete a difficult "Circle" attack minigame!
Flawlessly complete a difficult "Dodge" attack minigame!
Flawlessly complete a difficult "Line" attack minigame!
Flawlessly complete a difficult "Paddle" attack minigame!
Flawlessly complete a difficult "Slots" attack minigame!
Recolor five colors in one blow!
Collect 10 Thoughts.
Collect 25 Thoughts.
Collect 50 Thoughts.
Collect 75 Thoughts.
Convert a Thought into a Figment of Imagination!
Collect ALL Thought Upgrades!