There comes a part in the game where you enter a room that has two of the regenerating egg chambers filled with red biomatter. Destroy one of them and then make your way to the other. When you get to it, it will be exposed and you'll learn that it's a failed clone of Athetos.
At this point, shoot the clone and kill it. Once it is dead, this trophy will unlock.
Alternatively, you could let it live to get a different trophy.