Here is the full list of all 22 Galaxy Cannon Rider achievements.
Complete Crazy Circus.
Finish a ride using only one rider.
Pass through 20 rings of fire.
Reach Level 10 with 4 characters.
Do 3 eagles in one gameplay.
Reach level 10 with 6 characters.
Complete Sand Village.
Complete Icerim.
Complete Dagger Cliffs.
Complete Blue Bottom.
Complete Lost Jungle.
Complete Forge Fields.
Reach level 10 with one character.
Get 50 item boxes.
Reach 20 cannons further Crazy Circus' goal.
Reach 20 cannons further Sand Village's goal.
Reach 15 cannons further Icerim's goal.
Reach 15 cannons further Dagger Cliffs' goal.
Reach 10 cannons further Blue Bottom's goal.
Reach 10 cannons further Lost Jungle's goal.
Reach 10 cannons further Forge Fields' goal.
Unlock all worlds.