Garchomp is a beast. I mean, that is expected of any Pseudo-Legendary, but Garchomp takes it to another level. Of all the Pseudo Legends throughout the generations, only Garchomp has consistently remained in OU barring when it was banned from that to Ubers in Gen 4. No other Pseudo Legend can make such a claim, with only Tyranitar coming close, having finally fallen to UU in Scarlet in Violet.
And Garchomp's keys to success are its amazing stat spread and movepool with one of the more potent STAB combinations in the game. Base 103 Speed is key -getting the jump on so many base 100 Pokémon that are already considered fast to begin with is crucial with something packing Garchomp's power. And it is not just Speed. 108/95/85 defenses are well above average, meaning even uninvested, Garchomp can take a hit or two and invested it becomes a viable Tank in its own right, enabling even more mind games. Movepool is quite fantastic as well. Garchomp has a wealth of coverage to compliment its already complimentary STABs, leaving few if any truly safe answers into it while having access to Swords Dance thrusts Garchomp into a new Realm of Power, something you never want to hear on Pokémon with STAB Earthquake.
Even in Doubles this all around excellence carries over. Fast Rock Slides are amazingly good, considering the good coverage with Earthquake and potential flinches being game determinative, while having the bulk to stave of several spread attacks. If it wasn't for the fact that Landorus-Therian exists, it is very probable that Garchomp would have won more world Championships. And the current Doubles Meta is very favorable to Garchomp. Public Enemy #2 at the moment is Gholdengo, who Garchomp eats alive, as well as many popular Tera Steel Pokémon. Hydreigon's lower natural speed also makes it prey to Garchomp, as is the many other popular Dragon types. Clear Amulet is another amazing boon, protecting Garchomp from Intimidate ruining its own Attack. And Maushold's population bomb just makes fodder as Garchomp's Rough skin would eat that alive.
Garchomp does still have a few weaknesses. Its abilities can be lackluster compared to the competition and the amount of Speed Control running around makes Garchomp far more manageable when it isn't outspeeding the opposition. A quadruple weakness to Ice is a huge hit me sign on Garchomp's back that otherwise ruins its good bulk. Several popular Pokémon like Dondozo and Meowscarada have very favorable matchups into Garchomp and several of Garchomp's favored targets can win with Tailwind or the right Tera type. Garchomp still looks to be a beast going forward and must be respected all the same.
Land Shark Pack Attack
Ability: Rough Skin
Item Attached: Clear Amulet
EVs and Nature:
4 HP /252 Atk / 252 Spe
Jolly Nature (+Spe, -SAtk)
This Garchomp set functions rather simply as a fantastic attacker. Earthquake is incredible STAB in doubles, hitting both opponents for massive damage, though the friendly fire aspect must be accounted for. Dragon Claw is secondary STAB, but no less important in coverage. Many Dragon types are very popular right now, especially with the dearth of Fairies, so having a reliable answer into them, especially given that Garchomp natively outspeeds all of the them, is invaluable. Rock Slide has extremely synergistic coverage with Earthquake, lacks the friendly fire aspect and can pick up on crucial flinches. Protect is the best move in Doubles, hands down.
Clear Amulet protects against the stat dropping effects of Intimidate and Icy wind that may otherwise hamper Garchomp from doing its job.
Murkrow -Immune to Earthquake, has Tailwind to make Garchomp impossible to outspeed, Haze messes with Dondozo, what's not to love?
Hydreigon -the Special to Garchomp's physical with many of the same traits as Murkrow and terastalization can alleviate weakness stacking issues
Gholdengo -Earthquake weak, but enjoys Garchomp dealing with opposing Gholdengos and has an incredibly favorable matchup into Ice Attacks and Ice types.