Hippowdon as a counter
Hippowdon @ Leftovers
Ability: Sand Stream
EVs: 252 HP / 4 Def / 252 SpD
Impish Nature
IVs: 8 Spe
- Whirlwind / Stone Edge
- Stealth Rock
- Earthquake
- Slack Off
Hippowdon is a pretty good defensive mon, with reliable recovery, Stealth Rock, and phazing. A powerful STAB EQ also means it's got respectable offensive presence, and it even has access to Stone Edge (or Ice Fang if you REALLY want to hit Zygarde/Lando-T/Gliscor, but don't use that please) to nail incoming Mega Pinsir/miscellaneous Flying-types.
Hippowdon is naturally slow (base 47) but Stakataka is soooo slow that you actually want to lower your Speed IVs in order to better counter it. With the standard 31 Speed IVs, this Hippo spread usually gets 2HKO'd by +1 Gyro Ball after Stealth Rock (and you don't OHKO back without hazards most of the time).
+1 252+ Atk Stakataka Gyro Ball (104 BP) vs. 252 HP / 144+ Def Hippowdon: 196-232 (46.6 - 55.2%) -- 70.3% chance to 2HKO after Stealth Rock and Leftovers recovery
But, with 8 Speed IVs, Hippowdon reduces Gyro Ball's base power to 86, letting you easily dodge the 2HKO, while still outspeeding Toxapex.
+1 252+ Atk Stakataka Gyro Ball (86 BP) vs. 252 HP / 144+ Def Hippowdon: 163-193 (38.8 - 45.9%) -- guaranteed 3HKO after Stealth Rock and Leftovers recovery
You resist Stakataka's Rock STAB, so you take nothing from Stone Edge or Continental Crush.
+1 252+ Atk Stakataka Continental Crush (180 BP) vs. 252 HP / 144+ Def Hippowdon: 170-201 (40.4 - 47.8%) -- guaranteed 3HKO after Stealth Rock and Leftovers recovery
Fightium-Z is legit to lure Ferrothorn, but even +1 Fightium bounces off.
+1 252+ Atk Stakataka All-Out Pummeling (190 BP) vs. 252 HP / 144+ Def Hippowdon: 239-282 (56.9 - 67.1%) -- guaranteed 2HKO after Leftovers recovery
Meanwhile you do a ton back with EQ
0 Atk Hippowdon Earthquake vs. 252 HP / 0- Def Stakataka: 288-340 (88.3 - 104.2%) -- 25% chance to OHKO