the suspect reqs have been achieved, so I should hopefully be able to vote. If there is a more appropriate place to put this, pls tell me since this is my first suspect participation ever ;-;
With that out of the way, this is bluebim, formerly idekwhatneamtoyuse, here to give his 2 cents on Miraidon, which are that this bike lizard from the future has a ridiculously overbearing strain on not only teambuilding, but the battle itself. So averse are its effects that I believe it should be BANNED if the community wishes to foster a more balanced metagame to play (although it won't necessarily be as fun, a point I'd like to make)
What makes Miraidon exert so much pressure at every second is its damage output that supercedes even Mega Rayquaza, a speed tier that is only a smidge slow for it's liking, minmaxxed bulk that allow it to take uninvested super effective attacks from naturally strong pokemon like support Arceus-Ground (0 SpA Earth Plate Arceus-Ground Judgment vs. 0 HP / 0 SpD Miraidon: 270-318 (79.1 - 93.2%) -- guaranteed 2HKO), and tools in which it can either dispatch the VERY FEW pokemon that can take more than 2 hits from it, or use them to generate both momentum and an opportunity for its calamitously strong comrades to capitalize.
For those who don't believe me, here are some damage calculations against a max sp. def fairy. Mega Rayquaza's comparisons are done with a bold nature.
252 SpA Hadron Engine Miraidon Electro Drift vs. 240 HP / 252+ SpD Arceus-Fairy in Electric Terrain: 186-219 (42.1 - 49.6%) -- guaranteed 3HKO
This is the pivot set, inarguably Miraidon's weakest set in terms of firepower.
252 Atk Rayquaza-Mega Dragon Ascent vs. 240 HP / 252+ Def Arceus-Fairy: 160-189 (36.2 - 42.8%) -- guaranteed 3HKO
Here is a Rayquaza, with a speed boosting nature against the same mon but in phys. def.
Even without a boosting item, Miraidon's firepower means that it is most definitely going to 2HKO or outright OHKO any pokemon that doesn't have simply ridiculous bulk (chansey/blissey/ting-lu) or doesn't resist it. Dragon/Electric is a stab combination resisted by so few other type combinations and all of those fall to Overheat, if Miraidon is even running fire coverage. U-Turn can often just make pokemon like Iron Treads, Ting-Lu and Arceus-Ground momentum sinks for the defender, and opportunities to bring in either a suitable offensive mon like Koraidon or a defensive option that can continue to harrass the opposing team like Ho-Oh.
If Miraidon so chooses to run a boosting set or item not only does it's firepower increase to a point where it is ludicrous, but it also has immense variety in what moves and Tera typings to run to enhance it's wallbreaking/sweep capabilities. In this regard, it is perhaps one of the best Tera abusers in the game.
Miraidon's Double Dance set (Geomancy Xerneas at home), normally runs electric seed and Tera Fairy, but these can be changed easily. Life Orb can be used to allow an OHKO on Zacian at +1 with Parabolic Charge, Tera Ghost can provide an immunity to Extreme Speed, Tera Grass can be paired with Solar Beam to brute force it's way past Ting-Lu with Life Orb and turn Arceus-Ground into setup fodder, Tera Dragon to remove ground weakness and boost Dragon Pulse to downright hilarious levels of power. Weakness Policy with heavy defense investment and Tera Stellar behind screens deserves a mention, as while I have not played with it yet, the defensive investments ensure Miraidon both lives the hit, and gets a boost to it's offenses, which means it can hyperexpedite the loss with calm mind, or potentially be cheeky and run taunt to prevent phazing attempts mid sweep. When paired with the other monsters in the Tier like Scale Shot Koraidon, DD Arc-Ground, SD Zacian, Ekiller, DD or SD TR NDM, almost nothing is safe aside from building with hyperspecific pokemon and playing VERY WELL to outposition the enemy, which can be countered by the Miraidon user playing well themselves, or just utilizing the brute power of the aforementioned (Miraidon especially) to bowl over their defensive structures.
The Wallbreaker also deserves a mention as it is the most outright nuclear pokemon set I have ever laid my eyes upon. If paired with Taunt and Parabolic charge, the few brave stall teams stand no chance. Electro Drift when boosted with a Calm mind and Life Orb is the true definition of "nuclear power" while +1 Tera Dragon Life Orb Draco Meteor has a 50% chance to outright OHKO Ting-Lu unless it teras which is still beneficial to the Miraidon user so long as their other offensive pokemon are not damaged:
+1 252 SpA Life Orb Hadron Engine Tera Dragon Miraidon Draco Meteor vs. 252 HP / 252+ SpD Vessel of Ruin Ting-Lu: 471-556 (91.6 - 108.1%) -- 50% chance to OHKO
with a modest nature, this is outright guaranteed:
+1 252+ SpA Life Orb Hadron Engine Tera Dragon Miraidon Draco Meteor vs. 252 HP / 252+ SpD Vessel of Ruin Ting-Lu: 517-611 (100.5 - 118.8%) -- guaranteed OHKO
and a modest nature also grants Miraidon a little more flexibility in terms of using Tera to wallbreak, as modest life orb Draco will still do an insane amount of damage:
+1 252+ SpA Life Orb Hadron Engine Miraidon Draco Meteor vs. 252 HP / 252+ SpD Vessel of Ruin Ting-Lu: 387-458 (75.2 - 89.1%) -- guaranteed 2HKO after Leftovers recovery
Even against Hyper Offense, it's worse matchup especially if running a modest nature, it's power still allows it to leave huge dents in the makeshift defenses HO teams pack. Not to mention that it can turn to tera to alleviate these matchups, Tera Ghost and Fairy being the most prominent for Miraidon. One might argue that it then can't run Tera Dragon, but it's a risk you have to keep in mind as you try to revenge kill it.
Lastly, Miraidon's pivot set. HDB ensures that it can switch in and out freely, U-Turn generates momentum on the view things that don't instantly die when it clicks a move/it clicks the wrong one, and Taunt prevents set up/hazards/recovery which allows Miraidon to provide great value even as it's firepower is weakened. It can use various Teras like Steel/Ghost/Fairy or Dragon to enhance itself defensively or offensively.
What one might notice is that my description of the pivot set is rather lackluster compared to the hyperbole I've granted unto it's Double Dance and Wallbreaker sets. This is attributable to my lack of experience with it, and the fact that this set is the one being touted to be the most degenerate rather than the aforementioned both surprised me, and motivated me to vote that I should vote ban Miraidon if I sought a more "balanced" metagame (cough cough Koraidon)
The fact that my experience with other, more experienced Uber players is different enough that we have different sets we imagine as Miraidon's most dangerous yet all agree it is suspect worthy should be testament itself to just how dangerous each and every single Miraidon set is, and how it's flexibility, power and insane ability to capitalize on all aspects of Terastallization means it exerts far too much pressure on the teambuilder and battle. Only Koraidon has much immediate pressure in both of these aspects of building and playing, and even Korai has miniscule flaws that Miraidon does not, that being it's method of boosting and stallbreaking leaves it prone to priority picking it off and it's 4x weakness forcing it to tera to get rid of these. While Miraidon is not the ONLY reason that Ubers has become extremely volatile, it is undoubtedly the biggest reason why, and it constrains so much of teambuilding that:
1. It fulfills what I consider to be an AG worthy pokemon
2. It has made the tier rather boring, both in teambuilding and in playing it.
You can only really enjoy watching Miraidon do its best Xerneas, Z-Move or SS Tornadus-Therian impressions before you wonder if this thing is any good for the tier.
Non-offense teams have to use a combination of offensive pressure and defensive stability to block just ONE Pokémon concretely, and when paired with the other monsters that call this tier home, it can become far too easy for the offender to just break past them unless they misplay really hard. If the offender ever gets into a bad spot? Bam! Tera and they suddenly are at the driver's seat again, pushing the knife ever further.
While I due believe that forcing the tier to be in such a state where Balance is the best style as it was in SS is quite undesirable, we most likely won't reach this state unless we also ban Koraidon (which if this suspect's split is any indicator of, it probably won't be) and Last Respects (FUCK THIS THING REMOVE THIS SHIT). Even then, this tier is filled with many other monsters such as Tera Electric Kyurem-Black, Tera Fighting Zacian-Crowned, Dragon-Dance Necrozma, various Arceus-Formes, Chien-Pao and all of it's annoying variants. This, in my opinion, will be more than enough to ensure SV Ubers is a very different metagame from SS Ubers.
TLDR: I believe that Miraidon exerts far too much pressure on both teambuilding and within the battle itself which enables its dangerous teammates to a ridiculous degree. It is a wallbreaker unparalleled and can often just brute force through it's counters while still being fast enough to outspeed 90% of the unboosted metagame. Its flexibility through options like Taunt, Solar Beam, Dazzling Gleam, Overheat, Parabolic Charge means guessing wrong against it can mean a crucial part of your defensive core gone. It is an insane Tera abuser, setting up on and 6-0ing entire teams filled with mons that it has no business doing so like Zacian-Crowned or Kyurem-White. Or it could a pivot that switches in and out almost infinitely against passive teams while harassing them with Taunt, and still having sufficient power to force defensive plays that even if it doesn't do much, the pressure it exerted most certainly has.
Thusly, I will be voting BAN.
I do apologize if I ended up rambling about unrelated topics or whatever of the sort, but I truly do believe that the traits that define Miraidon has made it far too strong in the context of the metagame. Thus, I deemed it prudent to ramble on about them.
I would be rather sad if it went to AG. This thing made SV Ubers, especially pre-home, so much fun trying to learn.
Sayonara, Miraidon. You were among the greatest. Hopefully gen 10 nerfs you just right where you're enjoyable but not bannable.