Here is the full list of all 25 Jet Set Knights achievements.
Use Dash 100 times
Slay 5000 Monsters with Blade
Use 500x Voodoo Doll
Build 100x Guard Tower
Use Artifact-o-Matic Machine 100 Times
Defeat 10.000 Monsters
Find 500 Diamonds
Destroy 25 Training Dummies in Bonus Stages
Slay 100 Devils
Destroy 420 frozen monsters
Unlock All Artifacts
Slay the Muffin Boss
Die 100 Times
Destroy the Robot Boss
Shot 500 Fire Arrows
Slay the Snowman Boss
Shot 500 Ice Arrows
Unlock the Owl Artifact
Find 1000 Coins
Slay the Big Ape Boss
Shot 500 Arrows
Unlock All Minigames
Find the secret character.
Slay the Octopus Boss
Find the Legendary Monkey!