The way i did it was me and a mate plugged our controllers in using plug and play kits made sure auto shutdown was turned off and started an online game and then leave it for 10-15 hours (We did it over night and did it over 8 nights).
The achievement unlocks once the game has ended. - Thank you SRJB for confirming this.
We didn't build anything and had very few disconnections (if any it was due to my WP7 and because we don't live far from each other)
Then about 10-15 hours later the person that needed to lose, just sold there MVC.
Thank you HolyHalfDead confirming this: It has been reported that the games that got disconnected, count up to the point you get disconnected i.e if you leave it on for 10 hours and you get disconnected after 6 hours, then it only counts 6 hours.
Note by SRJB: I unlocked this after the game was over. If you have the 100, do one more short game and kill all your/their units and structures and see if it pops at the game over screen.
I would recommend losing if you need
I would recommend doing it on something other than versus so you can work towards
both pointless achievements but completionist like me want them all
Also if you are going to vote negative please comment to let me no why.