There's an easier way of doing this than making a frenemy play without scoring, which also works for people who, like me, have no xbox friends who are playing the game (or at least, playing the game in the same language), and it doesn't require a friend to lower their average score for your gain.
For this to work, you should have no online frenemies (which is to say, you just started the game and your xbox contacts are not playing).
Drop into a game and don't make any words. This works even when you drop in at the last few seconds, or if you drop in while the scoreboard of the last game is stil showing. Once the totals are shown, you'll get a list of the top players, and underneath a list of players near your own rank. You didn't make any words so you're down at the bottom, with others who just started but also with people who are just not good at the game. Click on one of them. This makes them a frenemy of you. Now just do your best in the next match and try to finish above that single frenemy you have that is also playing. Achievement unlocked.
I tried it this way because all my xbox contacts either don't have the game or aren't playing in my language, I found someone who proceded to rank below me in all matches that followed before I got bored of him showing up in my tables and deleted him again.