Gen 9 National Dex Monotype Assault Vest (Grass)

Hydrapple @ Assault Vest
Ability: Regenerator
Tera Type: Grass
EVs: 252 HP / 16 SpA / 240 SpD or 252 HP / 4 SpA / 252 SpD
Modest / Calm Nature
IVs: 0 Atk
- Fickle Beam
- Giga Drain
- Earth Power
- Dragon Tail
An Assault Vest set, or RegenVest set Hydrapple can use on Grass teams in Gen 9 National Dex Monotype. Assault Vest is useful for Grass teams as a Pokemon who can tank special moves, with Regenerator helping out with longevity. Hydrapple is useful as a partner for Grass teams using Ogerpon-Wellspring (or Waterpon). Fickle Beam is used for the Dragon STAB due to the chance of it doubling in power to deal more damage than Draco Meteor. Giga Drain is used for the Grass STAB since it allows Hydrapple to recover some HP, which is useful on an Assault Vest set. Earth Power allows Hydrapple to deal super effective damage to Steel- and Poison-types such as Gholdengo, non-Air Balloon Heatran, Iron Moth, and Nihilego. Dragon Tail is used for the last slot due to it being able to allow Hydrapple to force setup sweepers to switch out. Dragon Tail is also useful with the hazard stack from Ferrothorn and Brambleghast to make other Pokemon take chip damage switching in when bought in by Dragon Tail.
There are two EV spreads you can use for this set. I personally use the first EV spread listed of 252 HP / 16 SpA / 240 SpD with a Modest Nature. The 16 Special Attack EVs with Modest Nature gives Hydrapple a jump point in its Special Attack, giving Hydrapple's attacks some more power. The second spread of 252 HP / 4 SpA / 252 SpD is used with Calm Nature to give Hydrapple as much special bulk as possible.