It´s been a week and I´m still missing my last two Halo 4 achievements in my “Service record”.

Pump Yer Brakes - 1.25.2013
David and Goliath - 1.25.2013

Could you please help !!!

AFAIK, none of the new DLC Achievements show up in Waypoint - just XBL.

We are indeed working on a web issue where the Crimson DLC achievements do not show up. Never fear, if you have unlocked these achievements already, you won’t have to do anything further to unlock them on Waypoint. Once we’re able to fix this issue, your achievements will display correctly.