Bone Cracker

From Halopedia, the Halo wiki

Summary

Awarded after you kill an opponent by meleeing them in Multiplayer.

The Bone Cracker Medal is awarded for hitting and killing an opponent with a melee attack that isn't an assassination. It is available in all Multiplayer gametypes and has a Bungie difficulty rating of 3 (out of 10). It is represented by an inverted star with a fist. After you kill an opponent with a melee attack, a message appears on your screen that says: "You beat down (player)".