Here is the full list of all 38 Pile Up! Box by Box achievements.
Make a very big pile of 20 boxes or more
Smash every squash in the game at least once
Open every beach umbrella
Throw a pile of 10 or more boxes into the water
High jump: heavy dash and jump!
Complete Forest Fair 100%
Open the bonus route in Forest Fair
Watch a fireworks show with spiky friends
Complete Citizen Cave 100%
Watch a movie with upside-down friends
Fall to your doom 100 times
Open the bonus route in Citizen Cave
Build an autonomous flying box
Complete Frogipelago 100%
Put on a new outfit
Listen to a musical performance by some slimy friends
Destroy a pile of at least 10 boxes
Make a pile of 10 boxes or more
Make a pile of 5 boxes or more
Open the bonus route in Frogipelago
Bounce a trampoline... on another trampoline
Explore all of Boxling Square
Carry an item through 10 consecutive rooms
Long jump: dash and jump!
Finish the tutorial (no skipping)
Pick up every collectible in the game
Play every game in the arcade
Finish the game faster than the Seed By Seed record
Buy every costume
Scare every spider in the game
Complete a world without falling
Strike a pose on a pedestal
Move the wall of boxes in the cave to another room
Watch a performance by colorful friends
Open the bonus route in Feather Theater
Complete Feather Theater 100%
Do something horrible...
Unlock all other achievements