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