Here is the full list of all 18 Spiral Splatter achievements.
You have splattered 500 times
You have splattered 250 times
Congratulations, you've completed all levels
Congratulations, you've completed all levels with at least 1 star
Congratulations, you've completed all levels with at least 2 stars
Congratulations, you've completed all levels with 3 stars
Congratulations, you've unlocked stage 11
You have splattered 100 times
Congratulations, you've unlocked stage 10
Congratulations, you've unlocked stage 9
Congratulations, you've unlocked stage 8
Congratulations, you've unlocked stage 7
Congratulations, you've unlocked stage 6
You have splattered 50 times
Congratulations, you've unlocked stage 5
Congratulations, you've unlocked stage 4
Congratulations, you've unlocked stage 3
Congratulations, you've unlocked stage 2