Note - Make this class built to quickly kill your enemy.
Afteward, to host a private match or a split-screen match. Have a friend that's willing to be killed multiple times. If no one is willing, then use an empty player (a controlled player with no one actually controlling it). Start with Class 1 and allow your friend to kill you until Final Stand is activated. Then, have your friend shoot you into Final Stand. Once you are in Final Stand, activate One Man Army and switch to your second class. After you get up, start killing your friend. Every kill you get will count as a Last Stand kill as well as count toward One Man Army.