I have found the solution to rain and a good chuck of ou:
OUr Savor (Clodsire) @ Leftovers
Ability: Water Absorb
Tera Type: Fire
EVs: 252 HP / 4 Def / 252 SpD
Careful Nature
- Earthquake
- Toxic
- Recover
- Amnesia
This clod ignores most rain mons and from testing it's able to deal with a lot of top mons:
Gholdengo, specs Dragapult, Walking wake, Raging Bolt, Kyurem with tera, special Iron Valiants, Clefable, Darkrai, Ogerpon-Wellspring, Volcarona depending on its set, Enamorus, Primarina, Archaludon, Alomomola.
Its 1v1ed physical mons with and without tera like Valiant, Dozo, Barraskewda, Cinderace, and two different Kingambits (Don't ask how it won Idk)
Archaludon
252+ SpA Archaludon Draco Meteor vs. 252 HP / 252+ SpD Clodsire: 163-193 (35.1 - 41.5%) -- 77.3% chance to 3HKO after Leftovers recovery
252+ SpA Archaludon Flash Cannon vs. 252 HP / 252+ SpD Clodsire: 102-120 (21.9 - 25.8%) -- possible 5HKO after Leftovers recovery
+6 0 Def Archaludon Body Press vs. 252 HP / 4 Def Clodsire: 215-254 (46.3 - 54.7%) -- 8.2% chance to 2HKO after Leftovers recovery
Archaludon can't touch this clod, recover or set up on draco, immune to electro, flash cannon does nothing, standard av 6+ body press is a roll for 50%
Barraskewda
252+ Atk Choice Band Barraskewda Close Combat vs. 252 HP / 4 Def Clodsire: 155-183 (33.4 - 39.4%) -- 16.5% chance to 3HKO after Leftovers recovery
Without the rare option of coverage of crunch/psychic fangs, it does noting to this clod and will die to toxic eq
Kingdra
252 SpA Choice Specs Kingdra Draco Meteor vs. 252 HP / 252+ SpD Tera Fire Clodsire: 186-219 (40 - 47.1%) -- guaranteed 3HKO after Leftovers recovery
252 SpA Choice Specs Kingdra Ice Beam vs. 252 HP / 252+ SpD Clodsire: 170-202 (36.6 - 43.5%) -- 98.6% chance to 3HKO after Leftovers recovery
Rare rain option but still doesn't do too much
Ogerpon-Wellspring
252 Atk Wellspring Mask Ogerpon-Wellspring Power Whip vs. 252 HP / 4 Def Tera Fire Clodsire: 167-197 (35.9 - 42.4%) -- 93% chance to 3HKO after Leftovers recovery
Not really a good check to sd but can shrug it off when not set up and get a toxic off
Walking Wake
244 SpA Choice Specs Walking Wake Draco Meteor vs. 252 HP / 252+ SpD Clodsire: 222-262 (47.8 - 56.4%) -- 32% chance to 2HKO after Leftovers recovery
244 SpA Choice Specs Walking Wake Flamethrower vs. 252 HP / 252+ SpD Clodsire in Sun: 153-181 (32.9 - 39%) -- 8.5% chance to 3HKO after Leftovers recovery
Absolutely counters WW, recover/set up on draco
Raging Bolt
252+ SpA Raging Bolt Dragon Pulse vs. 252 HP / 252+ SpD Clodsire: 115-136 (24.7 - 29.3%) -- possible 5HKO after Leftovers recovery
252+ SpA Raging Bolt Draco Meteor vs. 252 HP / 252+ SpD Clodsire: 175-207 (37.7 - 44.6%) -- guaranteed 3HKO after Leftovers recovery
Recover/set up on draco
Kyurem
252 SpA Choice Specs Kyurem Freeze-Dry vs. 252 HP / 252+ SpD Tera Fire Clodsire: 62-73 (13.3 - 15.7%) -- possibly the worst move ever
252 SpA Choice Specs Kyurem Ice Beam vs. 252 HP / 252+ SpD Tera Fire Clodsire: 80-94 (17.2 - 20.2%) -- possible 7HKO after Leftovers recovery
252 SpA Choice Specs Kyurem Earth Power vs. 252 HP / 252+ SpD Clodsire: 214-252 (46.1 - 54.3%) -- 3.9% chance to 2HKO after Leftovers recovery
Specs earth power could be scary but one amnesia will make it a non issue
Dragapult
252 SpA Choice Specs Dragapult Draco Meteor vs. 252 HP / 252+ SpD Tera Fire Clodsire: 192-226 (41.3 - 48.7%) -- guaranteed 3HKO after Leftovers recovery
252 SpA Choice Specs Dragapult Shadow Ball vs. 252 HP / 252+ SpD Tera Fire Clodsire: 118-139 (25.4 - 29.9%) -- 0.1% chance to 4HKO after Leftovers recovery
Non issue, recover/set up on draco
Volcarona
Not gonna put calcs here because its an absolute set up war and there's too many, but with amnesia, recover, toxic, it can 1v1 most sets especially ones without tera blast.
I'm gonna stop listing cause this would get too long, but you get the point most of OUs top special attackers and rain mons get trivialized by Clod (All of these calcs are without any set up on clods side btw). Obviously it's not perfect and gets slapped by most physical mons including the top 2 (Kingambit and Great Tusk), Iron Treads on rain is a big one, and it physically can not Corviknight, Skarmory, and steel types with a balloon. But you aren't limited to one pokemon, teammates like Great tusk, Kyurem, Landorus, physically bulky mons, and anything that can deal with floating steal types/Iron Treads will pair perfectly. With teammates that can deal with these issues, it can 1v1 a good 70ish% of OU mons.