AlphaJax

For this, all you need to do is Win 10 games.

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, and before you put a word, click 'resign' in the bottom right corner. Do this ten times. Switch user to your main account, check your 'played games', and the achievement will pop.

If the achievement doesn't pop, exit out and restart the game. It should pop then.

Use this website: http://www.scrabulizer.com/

Unlike Scrabble-solver or any of the others, you can tailor it to Alphajax specifically. Not only that, but if you fill in the board with what your current game is, the Scrabulizer will actually work out the very best possible words you can play and list them in order of points.

This will get your average up and win you every game, unless the other guy has the Scrabulizer too

Playing this game will inevitably lead to many people randomly challenging you to games. You will find over time that a number of them did so just to get the Achievement for having 10 games active at the same time and have no intention of completing the match.

Scan through the "Their Turn" section to look for games that have been sitting idle for a week or longer. At this time, you can force an end to the game, and you will be awarded the (walkover) win regardless of the current score of the game. These wins count toward your win total for this Achievement. After forcing ten forfeitures, the Achievement will unlock.

UPDATE: DragonFangDan has had issues getting the force-quit method to give him the 10 wins for this Achievement. Can anybody confirm that this method will still work? (Solution was posted nearly three years ago, and this may have been patched out.)