Here is the full list of all 24 KnifeBoy achievements.
Reach The HeadQuarters!
Destroy 4 Bosses
Destroy 3 Bosses
Destroy 1 Boss
Kill over 600 Enemies
Kill over 400 Enemies
Kill over 200 Enemies
Collect at least 50 Pages
Collect at least 30 Pages
Collect at least 15 Pages
Collect 8 Golden Cogs
Collect 3 Golden Cogs
Explore 80% of the Open World
Explore 50% of the Open World
Collect 10 Feathers for the LizardMan
Collect 5 Feathers for the LizardMan
Kill 8 Rats using PowerSlam Attack
Slice 200 Enemies in Half
Collect all Power-Ups!
Collect you first Power-Up!
Complete 6 SideQuests
Complete 4 SideQuests
Break 100 Boxes
Break 40 Boxes