Go to your Safehouse (mainmenu - campaign- go to safehouse) and unlock and upgrade at the Cyber Core Station under martial Core "Overwhelming Force - Unstoppable Force" and don't forget to equip it before you start
mission 4 - Provocation on Recruit. After you are inside the mission, go left side, climb up and go forward until the little "open" area after the little stairs, here you see a door which lead in the next section, 5-6 enemies come out of the door, use your Unstoppable Force here.