I recommend doing this trophy on Chapter 16. Shortly after starting the chapter you'll end up on a roof there will be two guard you have to kill before you can let elena through the door you have to stealth kill them in order to get a grenade. After you let elena in, a car with several guards in it pulls up 4 of which hop out of the back this is were you throw the previously mentioned grenade.
Credit to: KittyGotWet for the video