"A mans true maturity should be based on how he acts when his identity is a secret."
Halo Reach is how a Halo should be. Simple, Fun, and Awesome. See you online.
Posted by: Tomvl117
But the archievement description says that you need to become a Sergeant but it doesn't say in one playlist...
That was before the update that gave each playlist it's own rank. Now you have to get 50xp in one playlist to get the achievement. Your highest 2 playlists are Social Big Team and Multi Team. Get one of those up to 50 and you should get it.