Gen 8 ZU
Bouffalant @ Leftovers
Ability: Sap Sipper
EVs: 248 HP / 56 Atk / 160 SpD / 44 Spe
Adamant Nature
- Substitute
- Swords Dance
- Head Charge
- Throat Chop / Earthquake
Substitute + Swords Dance set. Sap Sipper is the ability so you can freely switch into grass moves. Substitute allows you to potentially dodge status conditions and is useful for scouting. Swords Dance is for setting up. Head Charge is really powerful STAB. The last move depends on what you want to deal with. Throat Chop is coverage against ghost types, while Earthquake is coverage for rock and steel types. Do note, however, this set suffers from 4mss. (Fourth moveset slot syndrome) If you choose Throat Chop, you're pretty much walled by Rhydon. If you choose Earthquake, you're pretty much walled by ghost types.
248 HP EVs with 160 Special Defense EVs allows you to take a Volt Switch from Rotom well, as shown by this calc:
252 SpA Rotom Volt Switch vs. 248 HP / 160 SpD Bouffalant: 82-97 (20.8 - 24.6%) -- possible 6HKO after Leftovers recovery
44 Speed EVs allow you to outspeed minimum speed Tangela. The rest of the EVs are dumped into attack.