Wow this really sucks. I've done every campaign mission on heroic, some on legendary, except for the first one (the first REAL one, sierra 117) which I did on normal. So of course, I have the normal campaign achievement. But my disc got scratched and I can't load some maps. So now I don't have a few maps like isolation or high ground or valhalla. Which already sucks, but the only campaign mission I don't have is Sierra 117. So now I can't just go back and complete it in heroic, and its the only one I didn't do. And I'm missing out on 125 gamerpoints just cause of a scratched disc :C
I'm gonna borrow my friends halo later and complete, if he ever comes over :\