Moves
Quiver Dance lets Volcarona function as an effective setup sweeper thanks to its solid base 100 Speed and naturally high Special Attack. Fire Blast is Volcarona's strongest STAB move and has great neutral coverage, which is important to guarantee the OHKO against threats such as Landorus-T and Thundurus after a boost. Flamethrower gives up some of Fire Blast's power for accuracy, notably missing out on the guaranteed OHKO against Landorus-T after a Quiver Dance boost. Bug Buzz is Volcarona's secondary STAB move and lets it hit the Dragon-, Water-, and Rock-types that resist Fire-type moves. Notably, this is Volcarona's best move for hitting Cresselia, Hydreigon, and Tyranitar. Giga Drain is an alternative if Bug-type coverage isn't necessary, hitting Water-types such as Rotom-W and Suicune harder than Bug Buzz while preventing Azumarill from walling Volcarona and getting a free Belly Drum against it. The recovery it offers is also useful for keeping Volcarona healthy while it sweeps. However, running both Bug Buzz and Giga Drain is viable as well. Hidden Power Ice is preferred in the last slot to hit Garchomp, Mega Salamence, and Landorus-T, which notably allows Volcarona to more comfortably opt for Flamethrower, since it no longer needs Fire Blast to OHKO the last. Hidden Power Ground is an alternative that hits Fire-types that would otherwise wall Volcarona, such as Heatran, Blaziken, and Entei, though Volcarona needs multiple boosts in order to OHKO the latter two.
Set Details
Maximum Special Attack and Speed investment maximizes Volcarona's damage output while ensuring that it's as fast as possible, outspeeding Adamant Choice Scarf Landorus-T after one Quiver Dance boost. While it doesn't come into play often, the leftover EVs are placed in HP to give Volcarona an odd HP number, which allows it to switch into Stealth Rock twice. If you run Hidden Power Ground, 4 Special Attack EVs should be moved to Defense so that no EVs are wasted. A Modest nature is preferred to boost Volcarona's power further, since Quiver Dance boosts are enough to let it afford the Speed drop and the Speed boost from Timid isn't as useful. This also lets Volcarona OHKO Garchomp, Landorus-T, and Mega Salamence with Hidden Power Ice on the switch without needing to boost. Modest is also preferred if you're running Flamethrower over Fire Blast. Timid is typically inferior to Modest but lets Volcarona Speed tie with Mega Kangaskhan before boosting as well as outspeed Jolly Choice Scarf Excadrill and the occasional Jolly Choice Scarf Landorus-T after boosts.
Lum Berry is the preferred item to prevent Toxic and Thunder Wave users such as Cresselia and Thundurus from cutting Volcarona's sweep short; this also lets it function as an effective Klefki check. Focus Sash is an alternative that gives Volcarona a chance to set up against otherwise unsafe foes such as Hydreigon and offensive Zapdos if there's no risk of a priority user finishing it off later, and it also functions as a safety net against threats such as Jolly Choice Scarf Landorus-T and Jolly Choice Scarf Garchomp. Flame Body allows Volcarona to punish physical attackers that make contact with it, potentially crippling a dangerous threat such as Mega Kangaskhan or Mega Salamence as it goes down, which can give its teammates an easier time cleaning afterwards.
Usage Tips
Volcarona's goal is to sweep, so it'll usually be brought in after a teammate has been KOed or switched into something that can't hurt it much, such as Ferrothorn or Cresselia. If Volcarona tries to set up early, be sure that it has partners such as Choice Scarf Garchomp that can clean up in case Volcarona can't finish the job. Likewise, avoid setting up early if Volcarona is needed to beat a specific threat such as Cresselia, since it's typically used for the unique coverage that its Bug / Fire typing offers. Lum Berry makes it easier for Volcarona to set up against Pokemon that can only threaten it with status, so don't hesitate to set up against foes that can't do much immediate damage such as Porygon2 and Serperior.
Volcarona has very troubling matchups depending on its coverage move, but generally it should avoid setting up if the opponent has a Fire-type, since it can't hit most of them without Hidden Power Ground. Fire Blast is the move Volcarona should be using most of the time due to its huge power even without boosts; if you're running Flamethrower instead, this is still the preferred STAB move due to the superior coverage over its other moves. Bug Buzz should generally only be used against weakened foes and Pokemon that are weak to Bug or resist Fire such as Hydreigon, Suicune, and Tyranitar. Otherwise, it shouldn't be used unless missing Fire Blast is a big risk; even if Bug Buzz doesn't KO, the guaranteed damage can be more important, especially if a partner can pick off the foe afterwards.
Team Options
Mega Salamence creates an aggressive setup sweeper pair with Volcarona that boasts great defensive synergy, beating most Fire-types and Belly Drum Azumarill for Volcarona while appreciating Volcarona's ability to switch into Ice Beam and Fairy-types. Intimidate from Salamence before it Mega Evolves also helps Volcarona against physical attackers. Mega Kangaskhan appreciates Volcarona's ability to beat Steel-types such as Mega Mawile and Ferrothorn as well as Cresselia and the occasional Mega Sableye, while Mega Kangaskhan breaks down walls to let Volcarona sweep more easily. Volcarona also appreciates partners that can remove special walls like Chansey, so Mega Gengar makes for an effective partner by trapping and beating these walls. Cresselia can switch into most physical attackers that threaten Volcarona, such as Mega Kangaskhan and Mega Blaziken, while notably dealing with Garchomp, Landorus-T, and Mega Salamence if Volcarona lacks Hidden Power Ice. Cresselia also has Lunar Dance, which can give Volcarona a second chance to sweep.
Stealth Rock gives Volcarona an easier time sweeping, giving it a greater chance to OHKO threats such as Aegislash in Shield forme before boosts, as well as Mega Kangaskhan, Zapdos, and bulkier Thundurus at +1. Stealth Rock also cripples Talonflame, which completely stops Volcarona. Garchomp, Hippowdon, Landorus-T, and Mamoswine are all effective partners that can offer this support while being able to check Talonflame and other Fire-types to varying degrees. Hippowdon in particular can put foes to sleep or force them out with Yawn, which can help Volcarona set up. Grass-types such as Ferrothorn, Serperior, and Breloom deal with Water-types that give Volcarona trouble if it lacks Giga Drain. Ferrothorn in particular offers Stealth Rock support and a sturdy Rock-type switch-in for Volcarona. However, all of these are threatened by Fire-types, which Volcarona struggles against as well. Water-types such as Rotom-W, Greninja, Azumarill, Suicune, Cloyster, and Gyarados can take on the Fire- and Rock-types that threaten Volcarona. Volcarona can deal with any Grass-type for them, and Rotom-W in particular serves as an effective Talonflame check. Cloyster also pairs well as a setup sweeper alongside Volcarona, overwhelming slower teams. Electric-types such as Thundurus, Raikou, and Rocky Helmet Zapdos are also capable of checking Flying-types such as Talonflame and Mega Salamence for Volcarona.