Draw Slasher

Story related, cannot be missed.

Gunslinger is the boss at the end of Chapter 2. I actually found this to be one of the more difficult boss battles. You have to move from side to side in the arena, jumping over his cannon ball shots. While it is not difficult, the controls here are annoying, as your character frequently dashes instead of jumping, and if you try to trace too large of a jump circle, you get hit. In any case, once you overcome the controls, you can slash him once you reach the side of the screen. He will then move to the other side, and you simply rinse and repeat until his health is depleted.

Completing Chapter 2 will also unlock the next 2 Challenges (4-5).