For this, all you need to do is have ten games in progress at the same time.
You can do this with the use of a secondary profile, as you do not require a gold membership to play Alphajax online (as it is asynchronous multiplayer, free download, and on windows 8, instead of the 360).
Login to your second profile on windows 8. Challenge your main account to a game, but before you put a word or click resign, click the left-pointing arrow at the top left of the screen. Continue to do this by re-challenging and clicking the left arrow until the achievement pops on your secondary account. Then, switch to your main account, accept the games that have been sent by your secondary account, and then the achievement will pop. Having the games sitting there without being accepted won't work. Then, switch back to your secondary account, and then resign the games with your secondary account. Switching back to your main account after doing this will award you the following achievement, as well: