Hydreigon's moment to shine in the competitive meta for Pokemon Scarlet and Violet may have been brief due to the introduction of Paradox Pokemon into the pool of useable monsters for VGC Series 2. While the pseudo-Legendary creature was finally able to tout its strength as a competitively viable mon with the new mechanics introduced in Pokemon Scarlet and Violet, stronger Paradox Pokemon have made it all but irrelevant in the current meta. What was once one of the most used mons among competitive players has fallen by the wayside due to a number of factors that changed from VGC Series 1 to Series 2.
Historically, Hydreigon has been one of the least used pseudo-Legendary Pokemon due to its poor defensive typing making it 4x weak to Fairy types, a common offensive type in competitive battles. However, the introduction of Tera types gave it the chance to finally find usage in Pokemon Scarlet and Violet now that it could remove its disadvantageous typing when Terastallized. Although this gave Hydreigon a sizable role in the meta for Series 1 VGC, its reliance on Terastallization to be viable makes it outclassed by several Paradox Pokemon in the current meta.
Hydreigon's Time in the Spotlight Might Be Over
With the potential to be a powerful Special attacker, Hydreigon could take advantage of a few different Tera types to make it defensively viable. Steel is the ideal Tera type as it negates a weakness to Fairy types and turns it into a resistance while avoiding a weakness to Ground types with its Ability Levitate. Hydreigon also has access to Flash Cannon as a special move that deals STAB damage when Terastallized. Other than Steel, Fairy is another good Tera type since it removes the weakness to Fairy types while giving it the advantage over Fighting types, and Fire can be useful for powering up Heat Wave while eliminating two of its main weaknesses.
Unfortunately, Hydreigon needs to rely on its Tera type to be useful in competitive battles, and this means it's easily outclassed by other mons who don't have the same hindrance. Flutter Mane is the current most-used Special attacker in Pokemon Scarlet and Violet VGC Series 2, with a higher Special Attack and Speed than Hydreigon despite a lower overall base stat total. The Paradox Pokemon also has the type advantage over Hydreigon with its Ghost/Fairy typing giving it fewer weaknesses and more immunities than the Dragon/Dark type.
In terms of monsters with the same Dragon/Dark typing, Pokemon Scarlet and Violet's Roaring Moon is the better option than Hydreigon despite, once again, having a slightly lower base stat total. Although it's a physically-oriented attacker, Roaring Moon is capable of dealing more damage at a higher Speed than Hydreigon thanks to a useful combination of its Ability Protosynthesis, the held item Booster Energy, and the move Acrobatics. When Protosynthesis activates and uses up the Booster Energy, it can further increase Roaring Moon's Attack or Speed stat while also buffing the damage Acrobatics can do, making a Flying Tera-type Roaring Moon much more of an offensive threat than Hydreigon.
Hydreigon was in the best position it's ever been in regard to competitive viability with Gen 9's Terastallization mechanics. However, with Paradox Pokemon effectively pushing Hydreigon out of the meta, it's unlikely that this monster will ever see the same popularity it briefly enjoyed during Pokemon Scarlet and Violet VGC Series 1. Since it was only really useful when Terastallized, unless Pokemon Gen 10 introduces a new mechanic that can change its typing similarly, this may have been the most Hydreigon has ever been used in competitive battles.
Pokemon Scarlet and Violet are available now for Nintendo Switch.