…well, not quite all.
Hello 
Since Halo 4 I’ve got excited about playing Halo again and looking at some of the achievements I didn’t get for the previous games, they’re all regarding completing the game on Heroic or Legendary (or at all according to the one for Halo 3 but never mind) and the MM (which I’m not too fussed about)
So I’d like to tackle each game cooperatively on Legendary starting with Halo:Reach then Halo:CEA, Halo 3 and last but no means least Halo 4 (I don’t own Halo 2 or Halo 3:ODST anymore) It’ll give any of us a chance to get missing achievements (if you have any re: campaign) and play through all bar 1 of the Halo games in order and follow the story (if you enjoy that sort of thing which I do lol)
It’s a lot of work, going to take a lot of time and coordination (may have to set up a time when we can all do this) but I’d like to give it a try. If anyone is interested please respond to this post with general times that you are available and we’ll see if we can do this 
Cheers
CTID1981
> Count me in gt zillag22
Thank you
Added.
I’ll be online most of today (Sunday) and tomorrow (Monday) if you’re up for making a start on Reach 
Cool, I’ll be online in 1 hour
I’m up for reach and halo 4 done all achIvments let me know when (sorry no mic)
Ok, 16:45 UK Time I’ll have a co-op game set up for Halo Reach on Legandary starting at the very first level. Not sure how to invite though…
For reference, this was post was put at 16:25 UK time
I’m in if you want to add me. I’m ready now.
Thanks to PaulJ24, Zilagg22 and the cousin for helping complete up to and including Long Night Of Solace
One thing this has shown is that I’m not good enough to do this on my own lol
I’m back online tomorrow though the morning I’ll be on Halo 4 playing episode 7 of Spartan Ops but in the afternoon I’ll be free to pick up from Exodus hopefully til the end 
Feel free to add me and I’ll use this thread to put dates and times etc As per the OP the plan is to do the 4 Halo games I own (Reach, CEA, 3 and 4) all on Legendary to get the relevant achievements 
Thanks to PaulJ24 and his saint like patience, Halo:Reach has been completed on Legendary 
Next up is Halo:CEA and there seems to be a choc load of achievements with this one. For completing just one level on Legendary co-op you can earn Standard Operating Brocedure, Brovershield and Bro Hammer for a total of 80G. For completing the game in co-op legendary you can earn Birth of a Spartan, Believe in a Hero and Living Legend for a total of 80G.
In addition, looks like all the level specific achievements are available via co-op.
Let me know if you’re interested and when you’re available (I’m not around this weekend) 