Halo: The Master Chief Collection Message Board  

theoretically, its not super hard to get the par time completion. I have been doing it with legendary runs using the super damage ability. but also, you can do a run on normal using that ability and it can be done easily. Only difficult ones currently is Reach (no Super damage sadly) and Halo 4 atm (hopefully will get super damage soon)

You don't need to kill all of the enemies for par time, just get to the end as fast as possible and complete the final task. That's how we did it in the old xbox days before speed running and hacks, at least your immortal and don't need to worry about getting shot in the back 😉

What about the Spartan Ops cheats work but after completing, game still says last completed none and no achieve. Any ideas how to get the Spartan Ops progress to count and achieves pop?

Call Microsoft and tell them to take the EasyAntiCheat out of the single player modes. Or use Steam Achievement Manager. Almost all the Achiv's are tied to being online and having EAC active now.