17 Dec 2011 07 May 2012
There are two ways of getting this achievement. You can either go through them one by one and try and perfect yourself OR you can use a cheat to help you along.
For the cheat: In the Extras menu go to cheats and type in Quimbecile. This will unlock 42/44 stars but not the achievement straight away. You will be left with the first elimination challenge. Go play the first elimination round and if you get 4 stars you will recieve all 3 MI6ops achievements. If not and still complete the round you will unlock the first 2 achievements. For some help getting the 4 stars I recommend going to the top of the leaderboard and using some of the top scoring players' game set ups and you are sure to get it as at least 1 you will be comfortable with. (Personally I used a setup which had you kill less enemies)
For Alternative: Basically the same sort of deal. Take cover, use the auto aim with LT to your advantage, and try and complete it quickly as possible as time does add to your end score. Make use of the Leaderboards as they can guideline you of what set up you should use. Even when you can use someone else's set up you can adjust and tweak them to suit you.
If I have missed anything or could find anything wrong with this solution please let me know.
EDIT: You will get 44/44 stars with the code IF you've never played any of the MI6 Ops levels before. I suspect that you had played that one already, and thus the code didn't give you 4 stars on it.
I didn't play a single level before using the code, and I got all 44/44. Just had to play through one level after that (got a 1 star performance on it) and all three achievements unlocked at once. Credit to Taillear Dubh
Edit 2 credit to the dickish last commenter for his 'constructive' criticism. There has been a couple of people who have had their campaign progress glitch out on them. Although this never happened to me personally. So I suggest that you do this cheat after you are done with the campaign or do the cheat with an external memory device. If you are still unsure check out the comments below.