Call of Duty Infinite Warfare – Gravity Kills Trophy / Achievement Guide – Kill an enemy while floating in your own anti-gravity grenade. [Bronze / 15G]
Main Mission: Rising Threat
This is the first mission in the game. A few minutes into the mission you will enter a hostile spaceship. When you encounter the first large group of enemies look for a crate with anti-grav grenades. Throw such a grenade on the ground below you. While you are floating in the air kill an enemy.
There are many opportunities for this throughout the story. So worry not if you missed it here. Loadouts can be customized before most missions so you can bring anti-grav grenades with you.