Dedicated to Crimson - 80G (Original Achievement)
To get this Achievement you will have to clear all 5 Chapters in the first 5 Episodes.
You can play on ANY difficulty, therefor you can do this solo on Easy and get it without a problem. It may take a while to do it by yourself however, so you may want to invite some friends or join a boosting session.
Another thing to note is that when you die you will simply respawn, even if you are playing solo.
I suggest you go for other Spartan Ops related Achievements while going for this. 2 Birds, 1 Stone.