So I skipped the second chance mission in campaign to get the showdown achievement, I have gone back and replayed the mission but the game wont give me whatever camo completeing it unlocks, so I was wondering if anyone knows of a fix? Or am I gonna have to rewind campaign, which I really dont wanna do because I have all the challenges done.
Replaying missions doesn't unlock items that are "Unlocked after a later mission", Camos included. The only way to get that camo would be to rewind story, my friend.
Note, however, that as long as you use the "Rewind Story" feature in the Replay mission section, rather than "New Story" on the Campaign menu, your challenges will not be reset, nor will your unlocks. --- Gears of Halo 4: Black Ops II