Personally I hope there are no multiplayer related achievements. This is coming from someone who has every FPS Halo achievement (including Halo 2: Vista) except MCC and Halo 5: Forge (which is ironically because I need other people for the other achievements in Halo 5: Forge.)
It was a challenge yes but also incredibly luck based whether you could get some of the Halo 3 achievements (such as Two For One). These achievements often required boosting.
Halo: Reach launched without any “action specific” achievements, such as Two For One or Steppin’ Razor. Sure there were multiplayer achievements, like “Skunked” or “Be My Wingman, Anytime”, but nothing that required a specific weapon/map/enemy player situation to obtain. However, when the Map Packs started to launch this all changed, as it seemed they could only do multiplayer achievements at this point.
I remember the “All Alone” achievement being particularly annoying to get. You had to be the last man standing on a Defiant map pack map. The Defiant map pack launched with 3 maps, one was for big team/Team Slayer type games, one was Firefight, and it was only the third map that could be found in infection. To get this achievement, the matchmaking system had to randomly put you in a lobby where everyone had purchased the map pack (no small feat given Reach’s dropping popularity/population). And then at that point, you had to have the majority of people vote for Condemned, and even after that point, you had to pray to not spawn as the Alpha zombie 3 rounds in a row, let alone be the last man in the first place.
This level of luck required to get an achievement is frustrating and pointless.
Thankfully, when 343i’s first original Halo game, Halo 4, launched, it similarly did not have any “action specific” multiplayer achievements (except perhaps Bromageedon, but I suppose you could get this by yourself in split screen.) Now of course similarly to Halo: Reach, when Halo 4’s map packs started to be released, so too did the “action specific” multiplayer achievements.
But that was all a snapshot of the 2007 - 2013 years for Halo, when map packs had to be purchased.
With Halo 5: Guardians, there were no map packs to be purchased, as they were all given away for free (funded by the profits of REQ packs I imagine.) But this is the important thing to note - Halo 5: Guardians launched without any “action specific” achievements, and even when new achievements were added as apart of the Score Attack and Warzone Firefight updates, they did not include any “action specific” achievements as Halo: Reach and Halo 4 had done so before. (The hardest one would probably be Tour of Duty, as you need to randomly play all 6 maps. Finding a co-op partner to play the entire Halo 5: Guardians campaign could also be challenging as there is no split screen, but that won’t be a problem in Halo Infinite.)
To summarize all this, I do not want multiplayer “action specific” achievements to return, and given the trend from Halo 4 to Halo 5: Guardians, I don’t think they will. This is coming from someone who has earned them all.
That isn’t to say we can’t have armor locked behind achievements. Beating Halo 4 on Legendary to earn my Mark VI armor was fun and rewarding. But we shouldn’t have any armor locked behind achievements such as “Stick it to the Man! - Stick and kill the flag carrier with a Plasma Grenade in a matchmade game (only on an Anniversary map!).”
A good compromise could be have achievement requiring creative kills, but allow them to be unlocked in multiplayer OR campaign. Such as Halo 3’s “Two Close to the Sun - Destroy an enemy banshee with the spartan laser or missile pod in a ranked playlist or in campaign.” or “Fear the Pink Mist - Kill 5 enemies with the needler in a ranked free for all playlist or in campaign.”
Things like “Maybe Next Time Buddy - Board the same vehicle within 10 seconds after being boarded in any free for all playlist (Online).” should never return, unless they can be unlocked in Custom Games.