| S-[2] -> S-[4] | Historically I've thought Ho-Oh was better and that opinion hasn't changed. I'll discuss Ho-Oh a bit more below. It is still a great mon doing what it has always done and should remain S-. Nothing about Zacian-C itself has changed much. Yveltal has just gotten a lot better and it moves up something else has dropped.
| A [1] -> A[2] | The same thing I've said about Zacian-C applies to Arceus. This is a function of me rating Arceus-Fairy highly rather than anything significant changing with Ekiller. It doesn't like Psyspam, but it does like Basculegion. I have a slightly dimmer view of HO than some other people and the drop of one rank is a reflection of that. I'm alright with it retaining the top of A.
| A[5] -> A-[1] | So in Trios HO was spammed to the point where its representation far exceeded its viability. Mega Salamence, the HO staple, was brought just 3 times as of writing this (finals are yet to happen). It didn't actually come out in Anchor9s R1 game though the team it faced was such dogshit that it doesn't matter. Bodi brought it R2 where it trade with a Whirlpool Arceus-Dark. It would have lost that 1v1 anyways if Arceus-Dark ran a good set but this is the type of matchup where you'd expect Mega Salamence to put in a fair bit of work breaking and yet it didn't. Bodi also brought a BO no HO team. Xurkiyee brought in R3 on a HO v R8. R8's team is weird as hell but Mence is always going to struggle to sweep and to some degree break v these fatter balances, even if they're more standard. These sorts of teams usually have adequate means of preventing Mega Salamence from getting out of hand or punching too many holes in the defensive core.
Trios is a small tournament so I've also taken a look at seasonals rounds 7 and later as this was when the Xerneas ban came into effect. Xurkiyee brought Mega Salamence twice in R7. It wasn't really bad here. They really just lost this game purely due to luck. This was LO Zygarde which is a very fishy set that found a perfect matchup against someone who had never seen it. Mega Salamence went down because Outrage crit. Zygarde then lived a roll. The game was truly won by luck and a bad decision to Tera Yveltal. Even ignoring that Mega Salamence didn't really contribute anything. SD TR NDM pretty much solo'd Alphas team that the Xurk should have won the game with or without Mega Salamence. It could have gone crazy g3 if Xurk had just switched to it once Smeargle's sash was broken. Once webs were up it was pretty much gg, but a good showing for Mence if the game wasn't thrown. The only other apperance it made was Aninjadude v Squeeby. Mega Salamence fished for a Body Slam para, didn't get it and died.
So between these two tournaments Mega Salamence was brought 5 times in 65 games post Xerneas ban and didn't really do anything in any of them. Balance has trended a bit fatter and while it still can put in work v HO, it requires precise positioning and a decent matchup. The balance teams that Mega Salamence used to feast on with a little bit of chip are less common these days. After spending a while gathering replays Mega Salamence could justifiably drop lower than A-[1].
| A-[4] -> A-[6]/B+ | This one I'm a little less sure on. All of Palkia-O's previous problems still exist. It isn't good into HO and deadweight v stall. It can be s tier v a lot of balance teams, but it has to click the right move and that move has to hit. Palkia-O could potentially cling to A- due to metagame trends. As mentioned many times at this point, balance is getting fatter and this is something Palkia-O generally appreciates. These fatter balance teams are quite good against most of the meta. These fatter balance teams are also generally far worse into Palkia-O. It finds significantly more entry points v these fatter balances and is harder to force out. It should definitely drop, I'm just not sure how much.
| A-[6] -> B+/B | Honestly fuck building with this mon. You invest into defence to live LO Marshadow Shadow Sneak and still die to CB. Even then it doesn't matter because unless you face HO chances are this is your breaker and it is going to need to come and 3/4 of the time it dies to LO Sneak after rocks anyways. It suffers from Ultra Necrozma demanding attention in the builder and it loses to all the same stuff. It has absurd 4MSS. Without Fire Blast it is incredibly shaky v steels since defensive NDM is real again and FB is FB and MMY cannot afford to miss it. So it has one moveslot left to decide what beats it. FB beats Arceus-Dark 70% of the time and IB deals with Yveltal unless it happens to be Sucker Punch which is fairly common on offensive sets. Oh and now it can't stallbreak at all because Dozo walls it. If this were the end of MMY's issues it would probably be fine to stay at A-. It also gets outsped and OHKOed by Zacian-C and really struggles to break without a boost.
Ultimately you end up with this mon that is quite frail, has incredibly common counterplay that it doesn't reliably handle anyways, and requires a lot of defensive support if it isn't run on HO. It does have good matchups, especially v fatter balances lacking Zacian-C / Marshadow. Ultimately everytime I try and build with this mon end up using some other special breaker. Something like Specs Lunala is better into most non HO teams, requires similar if not less support, hits a lot harder, and actually scares its switchins even if it isn't scouted. Arceus-Dark and Yveltal are scared shitless of Moonblast and Ho-Oh worries about Trick or Tera Ghost 2HKOeing. Yeah and it can Tera Fairy to actually have a good defensive typing and doesn't crumple to a light breeze even if Shadow Shield is broken. MMY could honestly be B-, but I need to be realistic with noms.
| B+ -> B/B- | It isn't a bad mon at all. It only really fits well on HO and is not close to a staple on there. Usage is not the same thing as viability, but Zekrom isn't some stupidly strong mon that requires specific support or a breaker that teammates commonly rely on to help weaken shared checks. At some point results matter and Zekrom doesn't really have many to point to. Adem mentioned at some point it should be C+ and though I don't entirely disagree, it is a bit much for a mon that still has a place on HO even if it is used less than it should be. Zekrom is just really out of place in B+ and I'm a bit surprised that it didn't drop in the last slate.
| B -> C+/C | Everything I said a month ago still applies. If you want consistent screens go w Deo-S. If you want to fish go w/ Grimm. It isn't any worse currently than it was two months ago, it just should have dropped more than one subrank.
| B- -> C-/D | I'm going to assume that the only reason this didn't drop signifcantly further is due to the timing of the last vote. Yeah it is a good answer to LO YV, but that is all it does. It was justifiable when it also handled Xerneas as the role compression was quite valuable to fat balances. Yes it has a unique set of traits but Magearna rarely ever actually make use of them. C- is really just because D might be considered too big of a drop for one slate and countering LO Yveltal is maybe worth something. If it fits on good teams it is Gholdengo/Garganacl levels of specific.
| C+ -> C-/D | Every now and then it has the right four moves to actually do some work. Even that lightest of praise is probably overselling MMX. In the Xerneas meta you could handwave away its 4MSS to some degree as Stone Edge handled Yveltal and Ho-Oh and Giratina-O was uncommon. I don't see how you can do that now. Similar to Magearna, maybe there is some combination of moves that enables MMX to maintain a sliver of viability, but I just don't see it. It has probably 8 moves that it wants to run and even if it could run them all at the same time it would still be mid.
| C -> C- | Similar to Dozo this is a consistency thing. Melmetal should be the same subrank as Hatterene. I'm not a believer in TR so that is dropping it to C- though I don't care enough to argue against it retaining its C rank and moving Hatterene up a rank. Cresselia is not mandatory on TR like Hatterene is it being a subrank lower is fine even if Melmetal really wants Healing Wish support due it commonly running out of PP on DIB.
| C- -> D | Is being a mediocre suicide rocker for HO that is annoying for a couple of turns enough to justify ranking this. It is appealing as a breaker but it just a bit short on power to do that even with support while also having 4MSS. I've tried to make it work as a breaker and Landorus unfortunately just doesn't get it done consistently even with an entire team dedicated to supporting it. Yeah HO actually wants a mega sometimes, but Mega Diancie prevents Shuckle from getting up webs and Exca can get rocks up v TR teams. I'm struggling to see how that tiny niche is enough to keep it ranked.