Sword Kill

From Halopedia, the Halo wiki

Halo 5: Guardians Sword Kill medal.

Sword Kill is a medal awarded in Halo 4 multiplayer, Spartan Ops and Halo 5: Guardians Warzone for killing an enemy with the Energy Sword. It is represented by an energy sword silhouette on a blue circle atop a grey four-pointed star.