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