Set
Max Speed and Max special attack for that sweet sweet sweeping potential with sludge bomb. Hidden power ground to surprise Groudon-Primal when they think they can switch into this. Sludge Bomb OHKOs Clefable with inherited defense, Poison Jab doesn't. Knock off for ... knocking off stuff and Uturn for pivoting.
Calcs:
252 SpA Adaptability Beedrill-Mega Sludge Bomb vs. 0 HP / 0 SpD Xerneas: 452-536 (115 - 136.3%) -- guaranteed OHKO
252 SpA Adaptability Beedrill-Mega Sludge Bomb vs. 252 HP / 4 SpD Clefable: 484-572 (109 - 128.8%) -- guaranteed OHKO (inherited 120 HP)
252 SpA Beedrill-Mega Hidden Power Ground vs. 0 HP / 100 SpD Groudon-Primal: 146-174 (42.8 - 51%) -- 96.1% chance to 2HKO after Stealth Rock
252 SpA Beedrill-Mega Hidden Power Ground vs. 4 HP / 0 SpD Magnezone: 324-384 (114.8 - 136.1%) -- guaranteed OHKO
0 Atk Adaptability Beedrill-Mega U-turn vs. 0 HP / 0 Def Serperior: 300-356 (103 - 122.3%) -- guaranteed OHKO
0 Atk Adaptability Beedrill-Mega U-turn vs. 0 HP / 0 Def Tyranitar-Mega: 204-240 (59.8 - 70.3%) -- guaranteed 2HKO