I find it interesting so much discussion is being had around Iron Crown here, specifically the double dance set because I would argue it is easily the worst variant. DD Crown is mostly just a low/mid-ladder stomper where people struggle to play around activating its Weakness Policy. The set mandates screen support to be most effective, a playstyle has fallen off substantially and has more than enough adequate counterplay within the tier. Without the aid of screens it is far more easily chipped down and taking a super-effective hit usually brings it into range of any form of priority.
It is dependent on activating its item to be effective due to relying on Stored Power. If its WP is never activated then it requires at least 2-3 turns to be considered a scary enough threat. This just makes it susceptible to any form of neutral chip because it lacks any form of longevity, enough to bring it into range of many Pokemon.
Counterplay -
The tier has so much counterplay to this set assuming the matchup is played well and you don't activate its WP for free with a weak hit. I stopped at B rank so there is probably more especially if you factor in defensive Tera, particularly the popular Tera Steel. Correcthorse's post covers a lot of these also.
Phazers:
Garchomp forces the Tera Fairy at worse but it is a strong answer. Empoleon could not care less about the Pokemon and gets to spam Haze or Roar. Toxapex while being weak to SP easily pivots in to click Haze, with team support you can simply just whittle it down. Hippowdon is similar to Garchomp where it is bulky enough and can run Whirlwind. Ttar offensively threatens it and has the bulk to stomach Tachyon. Has access to Dtail and Roar also.
Encore:
HO has access to Lucha with a fast Encore and is faster if Unburden is activated. Ogerpon also being another candidate to do the same despite being slower than +2 Crown. Tinkaton doesn't take too much from Crown and can lock it into either a boosting move or Tachyon.
Unaware:
Tera Dark or Steel beats it.
Offensive:
Azumarill hits hard enough and has priority. Lokix is immune to SP and has strong priority/U-turn. Greninja resists both STABs though admittedly isn't amazing into Crown if screens are up. Bisharp, Scizor, and Excadrill can just boost alongside Crown and threaten to do way too much even behind a Reflect as Crown does not do enough without several boosts to threaten them. Metagross can break screens and then spam EQ to weaken it. Ursaluna just hits too hard, EQ does 70 min behind Reflect.
The King:
You don't beat Crown 1vs1 but you get to Twave it and chip it down or TP out into other partners
Even if Garchomp was booted from the tier we would still have more than enough means to limit this set. The only way I see it becoming an issue is if Focus Blast becomes popular enough over Tachyon, as it changes several of its matchups. Though running that move has its share of issues. Regardless I don't think DD Crown is remotely threatening enough right now and if anything Specs and Booster CM would be the main sets to keep an eye on.
It is dependent on activating its item to be effective due to relying on Stored Power. If its WP is never activated then it requires at least 2-3 turns to be considered a scary enough threat. This just makes it susceptible to any form of neutral chip because it lacks any form of longevity, enough to bring it into range of many Pokemon.
Counterplay -
The tier has so much counterplay to this set assuming the matchup is played well and you don't activate its WP for free with a weak hit. I stopped at B rank so there is probably more especially if you factor in defensive Tera, particularly the popular Tera Steel. Correcthorse's post covers a lot of these also.
Phazers:
Garchomp forces the Tera Fairy at worse but it is a strong answer. Empoleon could not care less about the Pokemon and gets to spam Haze or Roar. Toxapex while being weak to SP easily pivots in to click Haze, with team support you can simply just whittle it down. Hippowdon is similar to Garchomp where it is bulky enough and can run Whirlwind. Ttar offensively threatens it and has the bulk to stomach Tachyon. Has access to Dtail and Roar also.
Encore:
HO has access to Lucha with a fast Encore and is faster if Unburden is activated. Ogerpon also being another candidate to do the same despite being slower than +2 Crown. Tinkaton doesn't take too much from Crown and can lock it into either a boosting move or Tachyon.
Unaware:
Tera Dark or Steel beats it.
Offensive:
Azumarill hits hard enough and has priority. Lokix is immune to SP and has strong priority/U-turn. Greninja resists both STABs though admittedly isn't amazing into Crown if screens are up. Bisharp, Scizor, and Excadrill can just boost alongside Crown and threaten to do way too much even behind a Reflect as Crown does not do enough without several boosts to threaten them. Metagross can break screens and then spam EQ to weaken it. Ursaluna just hits too hard, EQ does 70 min behind Reflect.
The King:
You don't beat Crown 1vs1 but you get to Twave it and chip it down or TP out into other partners
Even if Garchomp was booted from the tier we would still have more than enough means to limit this set. The only way I see it becoming an issue is if Focus Blast becomes popular enough over Tachyon, as it changes several of its matchups. Though running that move has its share of issues. Regardless I don't think DD Crown is remotely threatening enough right now and if anything Specs and Booster CM would be the main sets to keep an eye on.