Update #2: Reasoning
RISES
S to S+
S- to S
S- to S
A+ to S-
A to A+
A- to A
B+ to A-
B to A-
B to B+
C to B+
C to B-
D to C
D to C
UR to C
UR to D
After already shaping AG around its Speed tier and power level since the second it was released, Calyrex-S has now managed to redefine the overall ceiling of the metagame by virtue of its Nasty Plot + Baton Pass set. With Necrozma-DM and Eternatus's nigh-mandatory status in the metagame, Calyrex-S has no issues setting up Nasty Plot boosts and forcing its only check in bulky Yveltal into battle. Calyrex-S can proceed to use this scenario to its advantage by using Baton Pass to bring out one of Eternatus, Xerneas, or offensive Yveltal. These three recipients are notoriously difficult to handle from a standalone perspective already, let alone with a Nasty Plot boost under their belt. This puts the opponent into a majorly disadvantageous situation, if not outright ending the match on the spot. Yveltal may still try to maintain some sort of momentum by using U-turn into the Baton Pass, but must risk being taken out by a Life Orb boosted Max Starfall in its attempt to do that, which also puts the Calyrex-S player at a great advantage. Given the recent popularity of these sets on all sorts of balanced and hyper offesive teams, as well as the fact that Calyrex-S is multidimensionally warping the metagame around itself with them, we have really come to a halt with respect to innovating sufficient counterplay to this Pokemon. This unimaginable grip is met with a rise to the uppermost echelon of the viability rankings.
Kyogre and Zacian-C are showing no signs of relenting any part of their grip either, becoming progressively harder to deal with as the days pass instead. Kyogre has massively shaken up its pool of checks with its RestTalk + Sheer Cold set, finding ubiquitous opportunities to fish for the OHKO on traditional checks in Ferrothorn and Eternatus with its great natural bulk and ability to use lots of passive Pokemon as bait. The sheer volatility of this set is incredibly hard to contain and faces to true counterplay other than Kyurem-W. Zacian-C hasn't undergone any significant set changes, but continues to exert non-negligible pressure on the metagame between its Assurance and Swords Dance sets preying on superglues in Yveltal and Eternatus. Both deservedly rise to S as a result.
Necrozma-DM is still close to mandatory on any team and it looks like that isn't about to change despite Calyrex-S's reign. The ability to check Zacian-C and Xerneas on top of compressing Stealth Rock support is simply not reproduceable by any other Pokemon. On top of that, Necrozma-DM is capable of disrupting many of its switch-ins in Groudon, Zekrom, Eternatus, and Ferrothorn with the ever-spammable Knock Off, making it a great deal less passive than one would expect. These qualities put it above its previous rankmates in A+ fair and square.
Despite its mediocre output in Snake so far, Groudon still rises a rank due to being impossible to wall outside of Lunala; even bulky Zygarde is almost always OHKOed by a Swords Dance- and Life Orb-boosted Max Quake. It is by far and away the most explosive means of taking advantage of Necrozma-DM, which is pretty important given the mandatory nature of the latter. Groudon + Zacian-C teams have been one of the faces of our metagame since as early as Kickoffs, making this a long-overdue rise.
Marshadow has recently picked up as a dangerous anti-meta wallbreaker, late-game cleaner, and wincon. Jolly Bulk Up variants are incredibly difficult to manage with the majority of Zacian-C not running enough Speed for it. Combine this with the fact that Calyrex-S is easily OHKOed by Shadow Sneak, and you're looking at the Pokemon that is actually in charge of Speed tiers in the current metagame. This forms a deadly combination with Marshadow's enormous wallbreaking prowess and ability to use Dynamax to its fullest potential. Most notably, Marshadow is capable of KOing Eternatus, which really is the best form of Marshadow-'counterplay' players are currently incorporating into their teams, after Stealth Rock damage and a Bulk Up boost with Max Phantasm in the majority of instances. Moreover, the amount of leeway Marshadow gets due to its unresisted STAB combination is pretty noteworthy as well, letting it just as well run surprise-techs such as Rock Tomb for Yveltal and Ho-Oh or Ice Punch for Yveltal, Zygarde, and Eternatus to pave the path for itself or a teammate. All of this amounts to a justified rise.
Lunala reclaims its previous spot on the viability rankings due to a multitude of factors. Firstly, Lunala is the only realistic and sufficient check to ginormous threats in Groudon, Zekrom, and Zygarde-C. This in itself is a very valuable niche that cannot be provided even remotely by anything else. Lunala boasts another crucial characteristic on top of that: it is immune to Shadow Tag. With Gothitelle surging in viability lately, this cannot be taken lightly. Combine all of this with the fact that Lunala can free up Yveltal's moveslot by running Defog itself and the fact that Tyranitar is nowhere to be seen these days, and it's not hard to see why bulky Lunala is a lot more affordable currently. Beyond its defensive set, Lunala has also made a splash as an offensive threat, distinguishing itself from Calyrex-S with the ability to lure and KO both Yveltal and Ho-Oh with Power Herb + Meteor Beam or Max Rockfall, and with its defensive uses.
As touched upon briefly in the reasoning for Lunala's rise, Gothitelle is once again proving that it cannot be taken lightly at all. The nature of current teams is really favorable for Gothitelle, between both Necrozma-DM and Eternatus or Ferrothorn featuring on the overmajority of them and being trapped fairly easily. This makes Gothitelle a potent tool of progress-making, subjecting the opponent to an inevitable game of guesswork that is never in their favor. There really is no other Pokemon capable of guaranteeing progress in such a fool-proof fashion, which leads to a rise all the way to A-.
Kyurem-W rises a stunning total of no less than three subranks. This is due to the realization of just how incredible Sheer Cold is and goes both ways. On one hand, Kyurem-W is a great abuser of Sheer Cold, finding opportunities to fire off multiple of them by forcing out popular Pokemon such as Kyogre, Yveltal, and Zygarde-C. On the other hand, Kyurem-W is also the best check to Sheer Cold Kyogre due to Ice-types being immune to the move. Beyond that, Kyurem-W is also just a great check to Kyogre on the whole, stomaching attacks from both Choice Scarf and Choice Specs variants with Utility Umbrella and forcing out Calm Mind variants with Sheer Cold or Dragon Tail.
Mewtwo has more potential than it is often credited for, being more than capable of busting through the tried-and-true core of Yveltal + Necrozma-DM + Eternatus with its stallbreaking Taunt + Will-O-Wisp + Recover sets or the combination of Nasty Plot-boosted Psystrike, Fire Blast or Shadow Ball, and Ice Beam or Thunder. The fact that most Zacian-C aren't fast enough to outspeed Mewtwo currently definitely adds up to its potential. Despite the popularity of Calyrex-S, we believed this was enough to salvage it from the C-ranks for now.
Hyper offense, whether that be standard Shuckle + Rapid Spin Regieleki Sticky Web or Dual Screens, continues to shine in the metagame due to the continued absence of Ditto and the constricted nature of the metagame making it very easy to counteract a majority of current builds with offensive overload. All of Shuckle, Regieleki, and Grimmsnarl rise as a result.
Landorus-T is a fairly underrated Dynamax sweeper on hyper offense, boasting an incredibly strong Max Airstream after a Swords Dance boost. With Intimidate, it can pretty easily use Pokemon such as Necrozma-DM, Zekrom, and Ferrothorn as setup bait. The fact that it isn't prone to Ditto lacking the ability to Dynamax due to Fly's two-turn nature is pretty noteworthy for hyper offensive teams as well, despite Ditto not being a common sight. Beyond all that, Landorus-T can also provide solid utility in Stealth Rock or Explosion support, and can act as a clutch soft-check to Groudon. It carves out a spot in C as a result.
Chansey is being reranked once again on the basis of its niche as a Xerneas check on stall teams that forgo Necrozma-DM for Quagsire. There's not a lot more to say beyond this.
DROPS
S- to A+
A- to B
B+ to B
B to B-
B to B-
B- to C
B- to C
C to D
D to UR
D to UR
D to UR
Zygarde-C drops a subrank due to Dragon Dance sets not being as defining anymore as they once were. This is due to the rise of two of its best checks; Rest Kyogre continues to enjoy immense popularity as a powerful wincon and Lunala has risen back to staple-status once again too. However, Coil sets are still really threatening and flexible presences, being great wincons on top of providing Glare support if needed. Dragon Dance sets should not be disregarded all of a sudden either, as they can still bust their way through Kyogre after forcing it to use Rest or with a few well-timed uses of Dragon Tail in conjunction with entry hazards. As a result, Zygarde-C finds itself a comfortable spot in A+ for now.
Neither Tyranitar nor Blissey are realistically affordable on the overmajority of teams. Tyranitar is just too much of a liability between an overreliance on Rest and Sand Stream hindering Necrozma-DM greatly. Blissey is uncomfortably passive in many instances, and detests Kyogre running Sheer Cold more and more often.
Giratina and Lugia drop a rank due to bulky balances and stall teams not being representative of the metagame. Both are too passive to fit on any other playstyle. On top of that, Lugia is directly outclassed by Lunala in nearly everything it may attempt to do, and can realistically only go lower from here.
Dracovish and Rayquaza have no realistic merit either. Dracovish really struggles to carve out a niche over Kyogre and Rayquaza faces fierce competition from just about any popular wallbreaker in any playstyle. Both provide next to no notable utility either, which further diminishes their chances at relevancy.
While Shedinja may appear to be appealing as a counter to Kyogre and Xerneas, the reality of the matter is that this isn't too notable of a niche that cannot be patched up sufficiently by much better Pokemon on just about any team or archetype. Dragon Dance Zygarde-C occasionally running Toxic and the fact that Shedinja always has to be on edge about Rocky Helmet Necrozma-DM if forgoing Poltergeist does no favors to it either.
None of these are realistically ever worth using. Amoonguss fails to check what it's supposed to check, i.e. Xerneas and Kyogre. Mew may seem appealing on hyper offense due to its access to moves such as Stealth Rock, Spikes, and Misty Explosion, but Spikes aren't in any demand on current hyper offensive builds. Umbreon may seem to have a niche in being somewhat of a check to Calyrex-S and Wish + Heal Bell support, but the teams that may find use in those niches are rarely ever seen.
UNDECIDED
S or S+
If you were to look at the slate, you'd see that Yveltal's rank was left undecided; half of us voted for S+ and the remaining half voted for S. Even after extensive discussions, the council wasn't able to reach consensus on Yveltal's place in the tier. Some of us argued that between its comically inflated usage in Snake combined with its sheer versatility and potency as an offensive threat, S+ was a realistic placement. Others argued that, while Yveltal definitely is a necessity on nearly everything, bulky sets are pretty passive overall and don't do a whole lot outside of checking Calyrex-S, while offensive sets, while flexible and potent, do not match up against Baton Pass Calyrex-S either. I've left Yveltal at S for now, with the caveat of bringing it up as a discussion point in the thread. If you believe you can make a convincing case for either rank, you should feel more than free to drop your thoughts in this thread!