Here is the full list of all 22 KUNAI achievements.
Kill 1 enemy.
Kill 300 enemies.
Defeat The Trasher.
Defeat The Guardian.
Defeat The Deprecator.
Defeat Furious Ferro.
Defeat Zensei.
Defeat Lemonkus.
Survive the airship attack.
Survive the police chase.
Capture SSD Floatanics Core.
Collect 4 heart pieces.
Find all heart pieces.
Find 5 treasure chests.
Find 20 treasure chests.
Explore 200 rooms.
Join the cool club.
Kill an enemy with a charged katana.
Kill a stunned enemy.
Buy an upgrade from the tabb store.
Buy all upgrades.