How to unlock an achievement if you did it in game?

How did you unlock the 60th level achievement then?

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The game would not recognise that achievement if you hadn't unlocked the previous one.

If certain achievements are bugged and not unlocking for lots of people all you can do is wait for the developers to patch the game like how the newest kingdom hearts game had problems with its achievements. Or maybe xbox is seeing another account of
massive amounts of achievements not unlocking like it did last month.

Sometimes it can take time for an achievement to unlock, it shouldnt but it does happen. How long ago did you complete the achievement?

Hello, thank you very much for the information.

I did not use any external means nor did I try to do so. I was playing a game and all of a sudden achievements started to unlock. I left as soon as possible but I ended up unlocking how 56 achievements of call of duty: Black ops 2

The achievement should still unlock but it won't unlock until well after you reach the target on the in-game tracker. But the achievement tracker for this game is not reliable and some of the achievements are still a little glitchy. So, to be safe, just
keep track of your progress with the in-game trackers and don't freak out when they don't unlock right away. As you play the game, not all of your kills will count towards the achievement. I never did figure out which kills did and did not count though.