Let It Rain

From Halopedia, the Halo wiki

HSA - Let It Rain.png

The Let It Rain medal is awarded in the Halo: Spartan Assaultand Halo: Spartan Strike campaigns for killing ten 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.