Grenade Spree

From Halopedia, the Halo wiki

HSA - Grenade Spree.png

The Grenade Spree medal is awarded in the Halo: Spartan Assault and Halo: Spartan Strike campaigns for killing three enemies in a row, with grenades, without being hit.

The medal is most easily achieved in the Windows version of the game, utilizing a mouse, as this control scheme gives the player far better grenade control than is offered by a controller or touch controls.