In specific areas in the game you'll come across exploding gas canisters of various kinds. Some look like propane tanks and come in different colors. Other ones look like the common helium tank for balloons found at a store or supermarket, and are long and usually orange. There are some good places to find enemies with explosives near them such as the large field past the concrete tube in Mission 4 "Nowhere to Hide" described by Mehtakcys. To use them you have to walk up to them, press
to pick them up, and then
to throw them after aiming with
. Then, a prompt will come up to press
to shoot them. If you get the timing and other factors right, you can get the canisters to explode right next to various groups of enemies. You need to kill a total of 10 enemies with these kinds of explosions. If you don't have the achievement yet, you can reload the checkpoint. Once you reach 10, you'll unlock the achievement.