Originally Posted by ferrari360max
Kill a group of 4 enemies with a grenade. (Single Player)
In the first mission *SNAFU* you will come to a courtyard and after dealing with the enemies in there a group of 4 will break down the door. Time your throw correctly and you can get all 4 of them easily. This is also pretty easy to do throughout most of the missions but obviously this is the best place.
For anyone else having trouble with this one as I was, try the very last mission, right before the end of the game when you set the third (and final) charge on the missile. A gate will open at the end of the room and 4 guys will start coming in, if you set the charge and quickly run and throw a grenade at the gate, it will blow them up before they get a chance to spread out. If you fail, just restart the checkpoint, clear the room, and try again. There are grenades in the room if you're out.
I couldn't get it with the tip above because it was just 3 guys that came out, and one guy that was in the back that I could never hit.
Thanks for the guide though, fairly simple (and thankfully short) singleplayer, and too many multiplayer achievements for how bad it is. But still appreciated.