Blastoise @ Sitrus Berry  
Ability: Rain Dish 
Level: 50  
EVs: 252 HP / 92 Def / 164 SpD  
Calm Nature  
IVs: 0 Atk  
- Muddy Water  
- Follow Me 
- Icy Wind
- Protect

Unown
Options:
- offensive: Scald
- supportive: Fake Out, Yawn, Flip Turn

Unown
Defensive calcs:
- 252+ Atk Excadrill Tectonic Rage (180 BP) vs. 252 HP / 116 Def Blastoise: 154-183 (82.7 - 98.3%) -- guaranteed 2HKO after Sitrus Berry recovery
- 252 Atk Urshifu-Single Strike Wicked Blow vs. 252 HP / 116 Def Blastoise on a critical hit: 93-109 (50 - 58.6%) -- guaranteed 3HKO after Sitrus Berry recovery
- 252+ Atk Mega Rillaboom Grassy Glide vs. 252 HP / 116 Def Blastoise in Grassy Terrain: 156-186 (83.8 - 100%) -- 6.3% chance to OHKO
- 252 SpA Transistor Regieleki Thunderbolt vs. 252 HP / 140+ SpD Blastoise: 150-176 (80.6 - 94.6%) -- guaranteed 2HKO after Sitrus Berry recovery
- 252 SpA Spectrier Never-Ending Nightmare (160 BP) vs. 252 HP / 164+ SpD Blastoise: 111-132 (59.6 - 70.9%) -- guaranteed 2HKO

Unown
Useful partners:
- set-up Pokémon: Mega Dhelmise, Mega Mawile, Mega Rillaboom, Mega Simisear, Landorus-T, Spectrier