Here is the full list of all 20 Jelly Brawl achievements.
Complete The Tutorial
Create a stage in the level editor
Complete 100 Rounds
Reach Level 5
Complete 1,000 Rounds
Reach Level 15
Complete 10,000 Rounds
Complete the Hit & Run Easter Egg
Get 50 Quick KO's
Complete 6 Unique Races
Reach Level 30
Complete 25 rounds as a Pacifist
Complete 100 rounds as a Pacifist
Collect 100 Coins
Collect 1000 Coins
Reach Level 35
Win 10 Races (Multiplayer)
Win 100 Challenge Rounds
Win 100 Boss Rounds
Reach Level 40