Not really enough players online to gain this legitimately, so chances are you will need to boost this. You will need 2 people to do this. Create a private match set to Time Wars, 5 minutes, and invite your friend in. There is really no quicker way of doing this as this game type requires you play the entire 5 minutes (I tried quitting out, and even though it shows a win, it does not count). Have whoever is working on their win wait until the final 15-20 seconds of the game and start seating people, as long as you show points on the board you will win when the timer runs out. Rinse and repeat 9 more times.
Find boosting partners here