Originally Posted by Shadow_Dog
So I beat all the chapters in the 5 episodes but it still did not give me an achievement. What can I do because I really do not want to replay all of them. TT
Did you not read the solution in the very guide you are posting in? Oh, how silly of me, of course you did...
Originally Posted by * Clueless *
Dedicated to Crimson 80
Completed all chapters in the first 5 episodes of Spartan Ops on any difficulty.
Infinity Multiplayer :: Spartan Ops related. Online Required.
Can be obtained on Easy+.
Complete all 5 chapters within all the 5 Spartan Ops Episodes either Solo or Cooperatively for a total of 25 chapters.
Glitchy: This achievement can be glitchy and won't unlock for some.
The Fix: Replay a mission Solo (Easy is fine) and it should unlock.
If played solo, do one mission in co-op. If played in co-op, do one mission in solo. Or if done in solo, try playing a mission again solo.
I bolded it so you can't miss it. Have fun.