Fracture

Right after they release this weapon to you, there will be a slew of enemies coming down the way to kill you and your comrades. Throw the Vortex Grenade right into the middle of the group coming down and watch the killing commence.

If you don't get the achievement after the grenade you're given, reload from the last checkpoint on the menu. There is a save right before you receive the grenade, so just keep reloading until you get it right.

Hi i didnt want to play through the level to find this location so what i did was go to the weapon testing place - go to the top of the map and pick up the vortex grenade - which is left on the dpad - then run back to the bottom of the hill to the red circle to make the enemies spawn - now wait for around 4 of them to spawn then throw it - WHILE STANDING ON THE RED Circle. if your lucky which u should be. it will spiral them all into the vortex and because your still standing on it. more enemies will spawn - meaning you will get the 5. good luck

a very simple and easy achievement all you do is go to dreadnought tower mission and you should first destroy a ship with the missile gun and shortly after that you have to grab a vortex grenade which is also when they introduce it to you so after you grab it you throw it perfectly in the middle of a group of enemies dont stand to close but you need 5 enemies or more to be killed if you dont get it after you throw the grenade press the back button and load the last checkpoint it takes you right back to when you are about to grab the grenade it took me about 4 times to get it right but its a fairly easy achievement