When I finished the game the first time I had 4 achievements that didnt unlock. Basic ones that should have come with game play. "Hell on Earth", "Crystal Craving", "Darn it, they keep breaking" and "Its a Magic number".
I tried a hard reset on the console hoping they would unlock when I started the game back up....nope. I tried uninstalling, clearing the save data and reinstalling. Nope....xbox auto updated the save data and I was stuck with a bad save or something.
Here is what fixed it. It sucks because you will have to start from scratch and replay the entire game but this is what did it.
I uninstalled and reinstalled the game. But this time I went into the settings, system, storage, highlight internal, press the menu button, view contents, go to "doom", hit menu button, manage game & add ons, toggle down to "saved data", highlight your profile save, hit the "A" button and select "DELETE FROM EVERYWHERE".
I started a new game, finished the first level and "Hell on earth" popped. Went to the doom fortress and did the first crystal and "Crystal craving" popped. So now I just have to work on the 666 kills and the 33 unique glory kills.
I will update this if those last 2 achievements unlock or not.