OK so this is something a bit different, and probably not that viable but here goes:
Jumpluff
Ability: Infiltrator
EVs: 252 Atk / 4 SpD / 252 Spe
Adamant Nature
- Seed Bomb
- Acrobatics
- Swords Dance
- Synthesis/Aromatherapy/Encore
The idea is you come in on Seismitoad, SD and then proceed to kill both of them. Jumpluff can kill toad with seed bomb even without a SD, but SD is preferable in case they decide to switch to Vileplume. Meanwhile the most that the toad can do to retaliate is easily recovered or (if they get lucky with a scald burn) healed. Vileplume is OHKOed at +2, and 2HKOed if Jumpluff hasn't boosted, while a sludge bomb from plume does not OHKO pluff, meaning you can switch in safely on a giga drain or sleep powder and kill plume if there are no rocks present (if you use encore and do switch in to something safe then gg plume). If you are worried about rocks, the speed EVs can all be moved to SpD to ensure that you don't perish.
252+ Atk Jumpluff Seed Bomb vs. 248 HP / 8 Def Seismitoad: 420-496 (101.6 - 120%) -- guaranteed OHKO
0 Atk Seismitoad Knock Off vs. 0 HP / 0 Def Jumpluff: 61-72 (20.9 - 24.7%) -- guaranteed 5HKO
+2 252+ Atk Jumpluff Acrobatics (110 BP) vs. 248 HP / 216+ Def Vileplume: 378-446 (107 - 126.3%) -- guaranteed OHKO
252+ Atk Jumpluff Acrobatics (110 BP) vs. 248 HP / 216+ Def Vileplume: 188-224 (53.2 - 63.4%) -- guaranteed 2HKO after Black Sludge recovery
0 SpA Vileplume Giga Drain vs. 0 HP / 4 SpD Jumpluff: 23-27 (7.9 - 9.2%) -- possibly the worst move ever
0 SpA Vileplume Sludge Bomb vs. 0 HP / 4 SpD Jumpluff: 218-260 (74.9 - 89.3%) -- guaranteed 2HKO
0 SpA Vileplume Sludge Bomb vs. 0 HP / 4 SpD Jumpluff: 218-260 (74.9 - 89.3%) -- 93.8% chance to OHKO after Stealth Rock
0 SpA Vileplume Sludge Bomb vs. 0 HP / 252 SpD Jumpluff: 170-204 (58.4 - 70.1%) -- guaranteed 2HKO after Stealth Rock
As I said not the best counter as you cannot afford to switch in on a sludge bomb from Vileplume, but Jumpluff is rarely seen so you might catch your opponent off guard (they might expect an encore SubSeed set).