Serperior - Solo - 7 Star Torterra Raid - Pokemon Scarlet/Violet

Rating: 9/10. No NPC requirements. Build details in description. Build created by @jksplays_gvo .
Original Video:    • Pokémon Scarlet & Violet: “Torterra, ...  

Serperior @ Shell Bell
Ability: Contrary
Tera Type: Grass
EVs: 252 Def / 236 SpA / 20 Spe
Modest Nature
Giga Drain
Leaf Storm
Breaking Swipe
Taunt

Vitamins: 25 Iron (or Resist Mochi), 23 Calcium (or Genius Mochi), 2 Carbos (or Swift Mochi)
Feathers: 2 Resist Feathers, 6 Genius Feathers

Stats at lvl 100 w/ perfect IVs:
HP : 291
Defense : 289
Sp.Atk.: 269
Sp.Def.: 226
Speed : 267

NPC Advantages: no requirements. intimidators (tauros, staraptor, arcanine), gardevoir (life dew), and drifblim (will-o-wisp) help.

Strategy: 2x breaking swipe, giga drain, taunt, terastalize, giga drain, wait for torterra to attempt and fail to use shell smash. 3x leaf storm, giga drain and/or leaf storm to victory.

Notes: The only change I made to @jksplays_gvo 's build was to move 20 EVs from SpAtk to Speed after I realized that it would allow serperior to outspeed torterra on turn 1 after it shell smashes, so that you can get the first breaking swipe in before taking any damage. Physical serperior can replace contrary, breaking swipe, giga drain, leaf storm, and shell bell with overgrow, coil, synthesis, leaf blade, and covert cloak. Special overgrow serperior can replace leaf storm with calm mind. Stellar (contrary) serperior can be either physical or special, using the same moveset for either one: tera blast, breaking swipe, synthesis, taunt.

Pros: supereffective tera type matching base type, excellent defense stat, great special attack stat, decent special defense stat, outspeeds torterra even after it uses shell smash. resists earthquake, earth power, and wood hammer. no weaknesses. taunt prevents torterra from using shell smash a 2nd time. breaking swipe debuffs attack 1 stage while charging tera orb. leaf storm and giga drain deals supereffective STAB (tera-boosted when terastalized) damage. leaf storm has 90 accuracy, 130 base power, and buffs special attack 2 stages (contrary ability inverts what is normally a debuff). giga drain has 100 accuracy, 75 base power and heals an amount equal to 50% of damage dealt. shell bell heals when attacking an amount equal to 1/8 of damage dealt. contrary ability causes torterra's use of earth power to have a 10% chance of buffing rather than debuffing 1 special defense stage.

Cons: poor HP stat