Since this seems to be kind of going for screens hyper offense with Gyarados and Grimmsnarl, I'll make the rest of the team fit that direction as well.
Grimmsnarl
Grimmsnarl is a solid screens setter, but I would use Tapu Koko instead. Tapu Koko can set up screens reliably as well due to its great speed stat, as well as being able to pivot out with Volt Switch or U-turn.
Tapu Koko @ Light Clay
Ability: Electric Surge
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
IVs: 0 Atk
- Volt Switch / U-turn
- Dazzling Gleam
- Light Screen
- Reflect
Volt Switch or U-turn pivots Tapu Koko out, and Dazzling Gleam is STAB. I prefer to use Volt Switch as it can do a large chunk of damage from the Electric Terrain boost and STAB but U-turn is also good as it lets Tapu Koko pivot out against common Ground types like Landorus-T.
Bewear
As a fighting type sweeper, I think that Hawlucha is a better fit here. Hawlucha appreciates Tapu Koko's Electric Terrain and screen support to let it sweep with more ease.
Hawlucha @ Electric Seed
Ability: Unburden
EVs: 252 Atk / 4 SpD / 252 Spe
Adamant Nature
- Close Combat
- Acrobatics
- Swords Dance
- Stone Edge
Electric Seed activates Unburden, and a Jolly nature isn't needed because of the speed boost from Unburden. Close Combat and Acrobatics are dual STAB, and Swords Dance lets Hawlucha boost its mediocre attack using its newfound bulk with screens and Electric Seed. For the last slot, I use Stone Edge to hit flying types like Zapdos but Taunt can also be useful against defensive Pokemon.
Frosmoth
Volcarona is a better Quiver Dance sweeper than Frosmoth. For Volcarona, I like to use a bulky Quiver Dance set.
Volcarona @ Heavy-Duty Boots
Ability: Flame Body
EVs: 248 HP / 156 Def / 16 SpA / 88 Spe
Timid Nature
- Quiver Dance
- Roost
- Flamethrower
- Psychic
This is the recommended Smogon set. 88 Speed EVs with a Timid Nature outspeeds neutral natured Landorus-Ts and Zeraora at +1. Flamethrower is STAB and Quiver Dance is great for setting up. Psychic hits Toxapex and Urshifu, and Roost is good recovery.
Gyarados
Gyarados is a solid physical water type sweeper. Another option is Azumarill, but the choice is up to you.
Gyarados @ Heavy-Duty Boots
Ability: Moxie
EVs: 252 Atk / 4 SpD / 252 Spe
Adamant Nature
- Dragon Dance
- Waterfall
- Power Whip
- Earthquake / Ice Fang / Bounce
Heavy-Duty Boots lets Gyarados not be chipped by Stealth Rocks. Waterfall is STAB and Power Whip is good coverage. For the last slot Earthquake is good coverage, but Ice Fang or Bounce lets you hit Grass types.
Azumarill @ Sitrus Berry
Ability: Huge Power
EVs: 4 HP / 252 Atk / 252 Spe
Adamant Nature
- Belly Drum
- Aqua Jet
- Knock Off
- Play Rough
Azumarill also benefits from screens increasing its bulk, allowing it to set up easily. 4 HP EVs activates Sitrus Berry after Belly Drum and Aqua Jet lets Azumarill move first. Knock Off is useful against slower steel types like Corviknight and Play Rough is STAB.
Dragapult
A Choice Specs set doesn't really fit on this hyper offense build, so another (niche) option is a Dragon Dance Weakness Policy set. Alternatively, Garchomp or Dragonite are good Dragon type sweepers.
Dragapult @ Weakness Policy
Ability: Clear Body
EVs: 252 Atk / 4 SpD / 252 Spe
Adamant Nature
- Dragon Dance
- Dragon Darts
- Phantom Force
- Sucker Punch
Dragon Dance is solid setup, Dragon Darts and Phantom Force are STAB. Sucker Punch provides priority, but Acrobatics could work as well.
A more reliable Dragon Dance sweeper is Dragonite. Due to its ability Multiscale and screens, it's pretty much guaranteed at least one Dragon Dance.
Dragonite @ Heavy-Duty Boots
Ability: Multiscale
EVs: 252 Atk / 4 SpD / 252 Spe
Adamant Nature
- Dragon Dance
- Dual Wingbeat
- Earthquake
- Roost / Extreme Speed
Dual Wingbeat is STAB, and Earthquake hits Steel types. Roost can be useful to activate Muliscale again, but Extreme Speed is a great priority move.
Incineroar
Incineroar no longer fits on this screens team, another Intimidate option is double dance Landorus-T.
Landorus-Therian (M) @ Leftovers
Ability: Intimidate
EVs: 252 Atk / 4 SpD / 252 Spe
Adamant Nature
- Swords Dance
- Rock Polish
- Stone Edge
- Earthquake
Swords Dance boosts Landorus-Ts attack even higher, and Rock Polish fixes its meddling speed. Stone Edge and Earthquake hits pretty much everything at least neutrally.
A safer option for Ground type set up sweeper is Garchomp.
Garchomp @ Life Orb
Ability: Rough Skin
EVs: 252 Atk / 4 SpD / 252 Spe
Jolly Nature
- Swords Dance
- Scale Shot
- Earthquake
- Stone Edge / Fire Fang
Swords Dance boosts Garchomps attack and Scale Shot lets it outspeed faster pokemon like Dragapult. Earthquake is STAB and Stone Edge is good coverage. An alternate option for Stone Edge is Fire Fang to hit Pokemon like Ferrothorn and Corviknight harder.
Pokepaste
