OU Doubles Sweeper
Sneasler (F) @ Mirror Herb
Ability: Unburden
Tera Type: Dark
EVs: 252 Atk / 4 SpD / 252 Spe
Adamant Nature
- Close Combat
- Dire Claw
- Night Slash
- Acrobatics
The strategy for this set is to have an ally use Swagger on an enemy, triggering the Mirror Herb to be consumed, giving a +2 boost to Sneasler's Attack. With the Mirror Herb being consumed, Unburden will activate, doubling its already insane Speed stat. Now that you caught your opponent off guard, you can sweep through their team, or at least a few of their Pokémon. One Pokémon that can fill this role is Grimsnarl, which has access to Prankster Swagger and Thunder Wave, which Confusion + Paralysis = Unfun time for the opponent
Tera Dark is what I recommend, as it turns Sneasler's 4x weakness into an Immunity, which can catch your opponent off guard. A more offensive option could be Poison, mostly to boost the power of Sneasler's Poison moves, as they may be shy from getting an OHKO. Adamant Nature is better than Jolly, imo, as Sneasler already outspeeds Max Speed Regieleki with the Unburden boost, so it's overkill to do so. Not to mention, it makes getting those OHKOs much easier
As for EVs, you can alter them to be more effective depending on what Pokemon are being used and which ones are. Sneasler is surprisingly bulky on the special side, for a Pokemon with such high Speed and Attack, at least, so points put into Speed can easily be put into HP or Sp. Defense instead to take some hits better
Close Combat is for Fighting STAB, although could be changed to Brick Break if you want to have a counter to screens, but due to being much weaker and thus not working very well with the Sweeping strategy. Dire Claw is for Poison STAB, and has a 50% chance to Poison/Sleep/Paralyze the target. Both Sleeping and Paralyzing the target can be very helpful and can come in clutch with the right luck. Some possible replacements could be Gunk Shot, due to it having a much higher BP, but only has 80% accuracy, which could be detrimental if it misses, thus I prefer the more consistent of the two (Also it has a 30% chance to poison the target). Another Option is Poison Jab which in terms of BP and Accuracy are the same, although Poison Jab has more PP, and has a 30% chance to poison the target. Poison isn't going to be as useful as Sleep or Paralysis, so unless you specifically want the Poison status, go with Dire Claw.
Night Slash provides Coverage, and STAB when Terastalized (See Dark Tera explanation). While there are other, more powerful coverage moves available to Sneasler, the Dark type can counter the Pychic types that pose a great threat against Sneasler's STAB moves. Tera Blast is another strong option, but provides almost no coverage when not Terastalized. If you choose a Tera type other than Dark, this slot becomes just a flex slot. Finally, the last slot can be any coverage move, but I recommend Acrobatics to take advantage of the doubled BP when you aren't holding an item, although this slot is easily flexible depending on the needs of the team. To name a few options; Swords Dance, Protect, X-Scissor, Rock Slide
TLDR: Swagger + Unburden combo makes Sneasler Go brrrr, Dark tera for Uno Reverse on Psychic, Close Combat, and Dire Claw are consistent STAB, leaving two slots for coverage.
