I had played the halo 4 campaign by myself on legendary, I got achievements for completing every level. However I did not receive any of the achievements of in-game unlockables for completing the game even on normal.
I looked at the achievements on the Xbox one system and it tells me I’m one level away from earning the achievement but halo 4 is telling me I completed all of the missions.
Yeah this has happened to me too earlier today! Go check out my post and I might be uploading a video to YouTube to prove it! Need to get this problem fixed ASAP man!
Xbox Live Gamertag: I AM FAZZA
YouTube: http://YouTube.com/GamerscoreTutorials
Ya I just beat halo 4 campaign by solo on legendary got all the achievements but Lone Wolf Legend!