Hedge-hopper

On the 'Frontline' level, kill every enemy Red Army and Fascist Soldier - the exact opposite of Invisible man. Sweep the whole level and make sure no soldier on either side is left alive before you finish. Because it's the inverse of the pacifist run, plan a separate aggressive playthrough (or chapter-select replay) for it. Comb the level so you don't leave one straggler.