assuming I starting from scratch again, this how i would do the campaign portion plus mm if curious, having actually already obtained all 7000g
Laso playlists(and pray to god my playlists dont reset again as they did at games launch) then Leg sub 3 houes. Or maybe the reverse/a mix. Either way this alone would get rid of a bunch in a single go. I would get every difficulty, plus the solo legendary in reach and 2. Plus the laso chivo for each, a playlist chivo, the laso laso master, and poasibly many random grindy “kill x amount of y” stuff and possible random other level specific stuff. Plus it wasnt too uncommon i got plenty of lar score or time chivos doing laso/3 hour legendary. Then manually go back and obtain every par score and time i didnt obtain. Why these first? Just to get them out of the way, and possibly be a glod chunk done with others as a side effect
So far, 2 full playthroughs, plus change as needed.
Full playthrough 3 would be Master Chief Saga, plus manually odst and reach normal playlist as theh are not in the playlist, and go for the achievement for beatinf that playlist, plus a cross game playlist, plus go for EVERY COLLECTIBLE AND LEVEL SPECIFIC ACHIEVEMENT POSSIBLE!
So we have 3 full playthroughs plus change down.
After this i would go in and get the few level specifics that are easier with a certian difficulty(or required) or set of skulls.
Again we are at 3 full playthroughs plus more change.
After this i would still need 1 or 2 playlists for each game/cross game, sp i would select the easiest/shortest playthroughs.
Between the 3 sets if “plus change” lets just call it the possible equivalent of 4 playthroughs at this point.
So, equivalent to 4 full playthroughs down, and we now have Spartan Ops. Since the save and quit method doesnt work any longer, i would manually just play theough spartan ops legendary. Dont recall ifnthey had easter egg or level specific chivos, bit if they did i would do them if possible, or via clena up.
So if we include Spartan ops as a “full campaign playthrough” we have “5 playthroughs plus possible change” and i cant imagine i would need go go back and grind “kill x amount kf anything”
At that point should be done with the story mode side. Onward to mm
I would only play h2a to grind out environmentalist chivo and h2a splatters first.
Next i would play ce and h2/h2a for legendary medals. I am unsure if the others work now or not but they did not at launch when I originally did this. They SAID they counted but unless i played ce, 2 or 2a they did NOT, because i could easily get legendary medals in 4 mm every 3 games on average but they never counted. So between getting h2a splatters, h2a enviornmentalists and legendary medals, i should also have a good chunk of others as well.
After that i would use forge to get the few forge chivos, and the seasonal/map specific stuff, and the weird soda can in h2a maps.
After that, i should only have stuff i would grind out by playing regular halo mm.
This is all off the top of my head having obtained all 7000, and a good chunk of that not being very efficient at the beginning.