I'd say covenant, so long as it's pre-schism.
They really lost their shit after that.

What time period? Because by halo 4, the covenant is pretty pathetic.

I think the Halo 2-3 Covenant where they were ruthless and not as simple to kill as in Halo 1, and not as predictable as in Halo 4 maybe Reach when they advanced without stop and not even dozens of Spartans could slow them.

Terrible idea, 2-3 was mass civil war time. By 3 they were broken. No, if you want them at their height then you want the covies leadiing up to the fall of Reach.

Ah yes.. On Reach they were unstoppable. when 1 elite died there was 10 more.

I feel like the reapers would win, but only after massive losses, and only because of indoctrination.

What about Master Chief VS. the reapers?

What, like, just Master Chief with no ship or anything?
Definitely Master Chief.

If Master Chief doesn't have a ship, he shoots a pilot and takes his.

Or the Covenant siding with M.C. as in the legions of The Arbiter of halo 3.
I have a hunch you will meet him in Halo 5 revealing that the former Covenant is at war with the remaining Covenant.
Probably that the fleet that aimed in for earth is just a fragment of the entire army, and that there are other systems with Forerunner planets and Halo rings. that the Humans were only one section.

Well, I haven't played Halo 4 so, halo 5 will have to wait.

Yeah, but 343 studios said that they wish to make another trilogy with 117. If there will be any other games like Reach, ODST and so on there is no info about. but they will try to make all the way to Halo 6.

Promethians if they have the composer. All the indoctrinated soldiers will be turned into more Promethians.

Agh! I feel sorry for whatever being that comes in the crossfire... imagine all 4 parts fighting each other. then the Humans with the Arbiters former covenant group just trying to protect their own asses

i cannot contain these epic images in my head.... it's about to explode.

Now add Samus Aran, 117 and the Arbiter kicking everyones asses