Here is the full list of all 30 10 Second Ninja achievements.
Finish Hard Mode and bleed the game dry for content
Finish every world.
Finish every world with 3 stars.
Finish the fifth world
Finish the fifth world with a 3 star rating
Drop a falling block on an enemy's head
Finish the fourth world with a 3 star rating
Wander around a level for its duration without murdering anything.
Finish the fourth world
Spend 5 seconds or more without touching the ground
Finish the third world with a 3 star rating
Finish the third world
Make an icicle fall on an enemy's head
Finish the second world with a 3 star rating
Finish the second world
Finish the first world with a 3 star rating
Kill two enemies with one shuriken
Toggle off the leaderboards OUT OF SHAME
Restart over 500 times.
Die over 50 times
Finish the first world
Go into the light.
Try firing your shurikens in a boss fight.
Shots... Shots Shots Shots Shots - die on spikes five times in a row
Finish a level with 0.03 or less from your next star rating (or 3 star the entire game)
Complete the tutorial.
Get your first star rating.
Press restart before the timer has even begun
Skip a cutscene.
Fiddle around with the settings.