time for some heat
Zapdos @
Rockium Z
Modest Nature
Ability: Static
EVs: 252 SpA / 4 SpD / 252 Spe
- Thunderbolt
- Heat Wave / Hidden Power [Ice]
-
Ancient Power
- Roost
What's Rotom's biggest draw? No common Electric-type can touch it (besides Thundurus-T). Do any of these Pokémon get a move that Rotom-H doesn't resist? Tapu Koko doesn't. Zapdos doesn't... oh hang on. Get up Rocks with your Hippo or Landorus. Bring Zapdos in and click Thunderbolt to chip Rotom into range on the switch. And then:
252+ SpA Zapdos Continental Crush (120 BP) vs. 252 HP / 252+ SpD Rotom-H: 102-120 (64.9 - 76.4%) -- 12.5% chance to OHKO after Stealth Rock
Boom. If it's an offensive Rotom then your job is even easier:
252+ SpA Zapdos Continental Crush (120 BP) vs. 0 HP / 0 SpD Rotom-H: 138-164 (110.4 - 131.2%) -- guaranteed OHKO
252+ SpA Zapdos Continental Crush (120 BP) vs. 252 HP / 0 SpD Rotom-H: 138-164 (87.8 - 104.4%) -- guaranteed OHKO after Stealth Rock
It can be tough to find a spare moveslot on Zapdos to do this effectively, but if Rotom is that big of an issue for you then you always have this ridiculously specific tech!