Kill 20 enemies in a row with only 1 health left (Individual)
This must be done without leaving an area and is best done early in the game. Reduce your health to one heart and kill 20 enemies. The Jungle areas are a reasonably easy area to do this in. Be sure to use your slide ability to daze enemies and take your time. If a heart spawns from an enemy or a jar that's blocking your path attack it until it turns into doubloons. Must be done by one player without assistance if playing Co-op