Death from Above

In the Battle of Sunaion, you need one Ground Pound that both kills a Grunt and smashes a grate. There are grated walkways over the water with Grunts on them - get above one, charge the Ground Pound in the air (hold the crouch/clamber button) and aim it at a Grunt actually stood on a grate. The slam kills it and breaks the grate together. Line one up properly and it's easy.