THE FINALS

The easiest way I can think to do this achievement is to have a frag, gas and Molotov equipped. Wait until the cash out is happening inside a building, therefore there is less room for enemies to manoeuvre and simply throw all three grenades inside the room one after the other when you know there are people in there. I managed to get a kill with my frag then gas and then Molotov. If you throw the Molotov into the gas, it will turn all the gas into fire which makes it easier.