Set:
Lets skip over the obvious ones (thunder and sticky web). Bug Buzz for the likes of Greninja, Hoopa U, Alakazam, Serperior, Tangrowth and the lati twins. 4th slot has some optional moves. Energy ball for mud mons (Swampert, Quagsire, Seismitoad etc.). Toxic to cripple walls and tanky sweepers (Shuckle, Groudon-Primal, Tyranitar, Buzzwole). Hidden power fire for Ferrothorn, Kartana and Scizor. Hidden Power Ice for Landorus, Garchomp, Gliscor etc. Hidden Power Steel is SUPER niche but works vs Diancie Mega, whos Magic Bounce stops webs from getting set up.
Calcs: (Even with 154 SpA, the damage output is meh for a mon that functions primarily for setting webs. It's still not overpowered in the slightest.)
252 SpA Galvantula Hidden Power Fire vs. 4 HP / 0 SpD Kartana: 256-304 (98.4 - 116.9%) -- 93.8% chance to OHKO (Inherited 120 SpD)
252 SpA Galvantula Bug Buzz vs. 0 HP / 4 SpD Serperior: 348-410 (119.5 - 140.8%) -- guaranteed OHKO
252 SpA Galvantula Bug Buzz vs. 248 HP / 252+ SpD Tangrowth: 212-252 (52.6 - 62.5%) -- guaranteed 2HKO (Inherited 120 SpD)
252 SpA Galvantula Hidden Power Steel vs. 0 HP / 4 SpD Diancie-Mega: 272-324 (61.6 - 73.4%) -- guaranteed 2HKO (Inherited 150 HP)
252 SpA Galvantula Energy Ball vs. 252 HP / 252+ SpD Quagsire: 284-336 (72 - 85.2%) -- guaranteed 2HKO after Leftovers recovery (Inherited 120 SpD)
252 SpA Galvantula Thunder vs. 32 HP / 0 SpD Kyogre-Primal: 270-320 (77.3 - 91.6%) -- guaranteed 2HKO
252 SpA Galvantula Hidden Power Ice vs. 244 HP / 108 SpD Gliscor: 332-392 (66.1 - 78%) -- guaranteed 2HKO after Poison Heal (Inherited 150 HP)
