Defeat a huge charging rabbit using only melee attacks,
without taking any damage from him.

This achievement is obtainable on the forbidden mines level. You encounter the rabbit about halfway through the level. Wait until the rabbit has an orange circle around him and he starts charging. Move out of the way and he will stun himself giving you time to hit him.
When he turns around you need to dodge quickly again.

Repeat until he is dead. Visual guide -