Halo: The Master Chief Collection

On this map there are several stalactites that are located above several places and serve as an alternative option for killing the enemy. The first stalactite can be found above the assault rifle turret, the second above the upper central platform, and the last above the frame behind the sniper rifle turret. To get the achievement, start a Custom Game with another player, where your opponent must stand under one of the stalactites. Shoot at the stalactite, it will fall and kill your partner. The achievement will unlock almost immediately.