I completed every single mission, on every single game, on Normal Difficulty on Halo: The Master Chief Collection for XBox One.
But the "Veteran" Achievement won't unlock, which is what you're supposed to get for beating all 4 games. Nor will the achievement for beating Halo 4. Yet it's there, on my profile, I can look though every mission of every game and they are all marked as been beaten on Normal on a Solo-Campaign...WTF Microsoft?! That was a lot of time and effort to beat 4 games.
And yes, I restarted my console, and ejected and reinserted the game before restarting it. Nothing.