What are good counters to Toxapex in OU?

Question

Title says it

Answer 1

I decided to answer because most of the Pokemon mentioned in the earlier answer are not currently available in DLC1 OU and Toxapex can be a tricky Pokémon to check and counter and it only has a handful of real answers. While there are Pokémon in lower tiers that can deal with it effectively, e.g., Celebi who can heal off status with Natural Cure and 2HKO Defensive Toxapex with Psychic, they have little viability in the current OU metagame as of DLC1. For this reason, I will limit my suggestions to OU viable Pokémon only.

The first Pokemon that comes to mind is Taunt / Nasty Plot Hydreigon.

Hydreigon @ Life Orb
Ability: Levitate
EVs: 252 SpA / 4 SpD / 252 Spe
Timid/ Modest Nature
- Nasty Plot
- Draco Meteor
- Flash Cannon
- Flamethrower

The first set uses Toxapex as set up fodder and there isn’t much it can do about it except for Haze. An unboosted Hydreigon has an 87.5% of 2HKOing physically defensive Toxapex with two Draco Meteors. A boosted Hydreigon Kos every Toxapex set and spread. But it should be noted that in actual gameplay, this set is prone to being worn down by passive damage inflicted by Scald Burns, Toxic, Life Orb Recoil, Stealth Rock, Sand/Hail damage and chip damage.

Hydreigon @ Life Orb/ Leftovers
Ability: Levitate
EVs: 252 SpA / 4 SpD/ 252 Spe
Timid/ Modest Nature
- Taunt
- Draco Meteor
- Dark Pulse
- Flamethrower/ Roost

This second set can only be worn down if Toxapex manages to poison Hydreigon. Otherwise Taunt completely shuts it down and it can proceed to wear down Toxapex. But It should be noted that this set isn’t very good in the current metagame.

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A more direct answer to Toxapex is Alakazam who is immune to status damage and has strong offensive presence. Though it is rather frail so should either pivot in or switch in during a status move.

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Trick Magearna is an effective answer to Toxapex but its ability to shut it down hinges entirely on a successful Trick. Otherwise all it can really do is use Volt Switch (Thunderbolt’s current viability on most Magearna sets is dubitable).

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Kyurem @ Choice Specs
Ability: Pressure
EVs: 4 Def / 252 SpA / 252 Spe
Timid Nature
- Ice Beam
- Draco Meteor
- Earth Power
- Freeze-Dry

or

Kyurem @ Leftovers/ Heavy Duty Boots
Ability: Pressure
EVs: 4 Def / 252 SpA / 252 Spe
Timid Nature
- Roost
- Substitute
- Earth Power
- Freeze-Dry/ Ice Beam

Freeze Dry Kyurem can give Toxapex a lot of trouble but does not appreciate Toxic as it is already prone to being worn down by entry hazards, unless it runs a Heavy Duty Boots set. In this way, SubRoost is a more reliable check to Toxapex and Choice Specs outright KOs defensive variants (the good variants) with Freeze Dry.

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Dragapult @ Spell Tag
Ability: Infiltrator
EVs: 252 SpA / 4 SpD / 252Spe
Modest Nature
- Hex
- Thunder Wave/Will-O-Wisp
- Draco Meteor
- Substitute/U-turn

Hex Dragapult is also a good check to Toxapex especially if it runs Substitute and Thunder Wave over say Will-o-Wisp. In this way it can more readily rely on Parahax to break Toxapex and deal heavy damage with status boosted Hexes.

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Magnezone can switch in to Toxapex for free, but should be wary of Scald burns, not that they inflict a lot of damage in gen 8.

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Excadrill poses an immediate threat to Toxapex but does not appreciate Scald or its burns.

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Slowbro @ Rocky Helmet
Ability: Regenerator
EVs: 252 HP / 252 Def / 4 SpD IVs: 0 Spe
Relaxed/Bold Nature
- Scald
- Slack Off
- Teleport
- Future Sight

Future Sight Slowbro is an excellent Toxapex lure. With smart playing it can lure Toxapex into a turn when Future Sight lands. Alternatively, Psychic smacks Toxapex more directly. You should be wary of Toxic, however.

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Toxapex cannot switch into Adamant Banded Wicked Blow Urshifu as this always 2HKOs every set and spread.

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Sub/Heal Bell Nasty Plot Togekiss demolishes Toxapex and there isn’t much it can do to it because Togekiss’ Flinch rates are usually enough to break Toxapex. Additionally, Togekiss is just really good right now.

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The last mon I can think of is really niche and very gimmicky, but if you really hate Toxapex and its defensive core members (Ferrothorn, Amoongus etc.), Sap Sipper Whirlpool Perish Song Azumarill functions as an excellent lure to its typical switch-ins.

Answer 2

This is what Smogon says for SM, I’ll do SWSH too.

Checks and Counters

Psychic-types: Pokemon such as Tapu Lele, Latios, Mega Gallade, and Mega Alakazam all are capable of doing major damage to Toxapex, though none of them appreciate being worn down by poison or burn. It's worth noting that if Alakazam stays in its base form, it will not be affected by residual damage. Reuniclus gets a special mention thanks to Magic Guard preventing it from getting worn down and it being able to threaten Toxapex with Psyshock.

Electric-types: Electric-types such as Tapu Koko, Zapdos, and Mega Manectric all threaten Toxapex with their STAB moves, with Zapdos being particularly effective against Toxic Spikes variants due to its access to Defog. Zapdos is also impossible for Toxapex to significantly cripple unless it's running Toxic.

Ground-types: Landorus-T, Garchomp, and Gliscor all are capable of heavily damaging Toxapex, though none are safe switch-ins by any means, with the first being weak to Scald and Garchomp being vulnerable to burns.

Taunt: Taunt is a good way of shutting down Toxapex, as it can only use Scald to fish for burns. Taunt Tapu Fini is particularly bothersome because it clears Toxic Spikes with Defog, is immune to status until Misty Terrain wears off, and heavily chips away at Toxapex with Nature's Madness. Whirlpool variants, in particular, trap and outright eliminate it. Other Taunt users such as Gengar, Tapu Bulu, and Gyarados are also effective means of shutting Toxapex down and taking advantage of its passivity.

For SWSH, Smogon doesn’t have a counters list sooooo....

Poison types shut down Toxapex’s poison stall strategy, and so do steel types. Scald cripples physical attackers, so a special attacker is better. Digging through some stuff, I think Whimsicott can take on Toxapex. It gets priority Taunt, and most Toxapex don’t have poison moves, being walls with only Scald for burns. Whimsicott resists Scald, and a burn won’t affect it much, since it usually carries special moves.

So yeah that was my own evaluation.

Hope this helps! :)