Three words: Hawlucha is back.
Though, to elaborate, I believe VoltTurn Offense is viable now, too.
With a terrain setter that is more than just fodder in the tier and the tier not necessitating Physically defensive Toxapex, Hawlucha is back with one hell of a vengeance, able to completely dismantle teams when given the perfect opportunity. While Bulu served as a fine terrain setter for it before, Rillaboom is a much greater support Pokemon when it comes to setting its terrain, being able to provide Knock Off support, Leech Seed, and pivoting for its team. Additionally, with access to the reliable Close Combat, Hawlucha no longer needs to risk a game-losing HJK and can just cleanly sweep teams when the opportunity arises. Though, with Hippowdon here to harass it, I've enjoyed running Taunt as a last move to prevent Toxic/Whirlwind, as its STAB moves provide it magnanimous coverage as is.
Hawlucha @ Grassy Seed
Ability: Unburden
EVs: 240 HP / 252 Atk / 16 Spe
Adamant Nature
- Swords Dance
- Acrobatics
- Close Combat
- Taunt
Specifically, this set is super nice. It has enough speed to outspeed Sand Rush Excadrill after Unburden, and has the aforementioned Taunt to turn its checks in PhysDef Pex and Hippowdon into setup fodder. Aegislash is the only thing in the tier that genuinely walls it, but running Libero Cinderace/Rotom-A on VoltTurn Offense really helps it a lot. All in all, I highly suggest giving this set a shot if you opt to run Seed Hawlucha.
Though, Gen 7 has already demonstrated to us the raw potential of Hawlucha's cleaning abilities under a terrain. Let's talk about the much more interesting Rillaboom.
Despite what it seems on paper, from what I've seen and played, I don't believe Rillaboom is really all too fit as an offensive Pokemon in the tier due to the prevalence of natural Grass resists such as Corviknight, Rotom-Heat, and Ferrothorn. While it has some neat options, strength, as well as a terrain to back it, I've found it serves much better as a defensive pivot. While its pure Grass typing lets it check Excadrill (especially with its terrain) and Rotom-Wash, it also has fairly respectable bulk of 100/90/70. Though, most prominently,
it has a great supportive movepool. Support moves consisting of Drum Beating, Knock Off, Leech Seed, and Taunt give it great options to disrupt the opponent and support its team, however, its access to U-Turn lets a defensive variant perform especially well on VoltTurn Offense archetypes along with Libero Cinderace and Hawlucha as an opportunistic cleaner. With these great options and circumstances, the archetype is startlingly solid at the moment with Libero Cinderace now freed, and without Dracovish to harass it every which way.
Rillaboom @ Leftovers
Ability: Grassy Surge
EVs: 252 HP / 200 Def / 56 Spe
Impish Nature
- U-turn
- Drum Beating
- Knock Off
- Leech Seed / Taunt
I've been running this set to great success. It has enough speed to outspeed Neutral Aegislash, and is specked to soak physical hits and support its team. The last slot is fairly interchangeable, but I've enjoyed Leech Seed to sustain my team along with Grassy Surge. It works surprisingly well.
Rotom-Wash is now freed as well, and without Seismitoad being of any more real relevancy, it works to a great effectiveness on VoltTurn, being able to completely destroy Hippowdon and act as a great breaker with access to Plot, performing similarly to Heat, and maybe even to a greater effectiveness. It works very well with Hawlucha, too, for its ability to break apart its potential defensive answers, and form a good pivoting core with defensive Rillaboom.
https://replay.pokemonshowdown.com/gen8ou-1125587882
Here's an example replay of how I believe the new era of VoltTurn would work, at least with Hawlucha variants; you pivot around, wear away at your opponent, and eventually, you find a good opportunity to get your terrain up and get Hawlucha in. Even in impossible seeming scenarios, Hawlucha is capable of completely breaking apart the foe if you find a good opportunity, which VoltTurn has always really been able to scout for, especially now with Rillaboom.