While a majority of the answers you would first think of are taken, I can still think of an answer that finds it's niche as a
counter which fits on hazard-stack teams without any other answers to threats like kabutops and qwilfish,
physically defensive poliwrath.
Poliwrath @ Leftovers
Ability:
Damp
EVs: 252 HP / 252 Def / 4 SpD
Relaxed Nature
- Circle Throw
- Scald
- Rest
- Sleep Talk
Yes, I know water absorb is the preferred ability usually, however consider this: Everybody assumes poliwrath uses water absorb unless it is on rain teams. Because of this, it is impossible for the opponent to know you are using damp and is willing to risk using a water move into poliwrath unless you have revealed damp earlier in the match, or accidentally switched in on a water attack. It is like the idea of using heatproof bronzong in ru, but even better because poliwrath resists water attacks anyways and doesn't lose terribly much by taking damp instead.
With that out of the way, the benefit of damp is that you don't die to explosion from qwilfish, making this a counter. This is even more the case when you realize that in a match, the two most likely scenarios when switching into qwilfish is switching into either poison jab or swords dance. if qwilfish uses poison jab, it does
252+ Atk Life Orb Qwilfish Poison Jab vs. 252 HP / 252+ Def Poliwrath: 113-134 (29.4 - 34.8%) -- 100% chance to
4HKO after Leftovers recovery
and then you get to immediately phaze qwilfish out with circle throw, both removing the threat temporarily and stalling a turn of rain dance. After circle throwing, you will have close towards 50% of your health. If qwilfish uses swords dance, it is at +2 and from there one of two things happens. The first thing that could happen is that qwilfish uses poison jab at +2 before you circle throw, it does
+2 252+ Atk Life Orb Qwilfish Poison Jab vs. 252 HP / 252+ Def Poliwrath: 224-265 (58.3 - 69%) -- guaranteed
2HKO after Leftovers recovery
and then qwilfish gets phazed out. This is fine and in this scenario you just have to play smart later in the match and get poliwrath reasonably healthy again or set the pace of the match in such a way qwilfish doesn't get another chance.
However, qwilfish does not know you have the ability damp. If qwilfish uses explosion, you get to phaze qwilfish out without taking any damage. This is the best scenario possible.
In any other scenario possible, qwilfish does not do anything substantial to poliwrath and it gets phazed out. Like I said, this counter finds its niche on
hazard-stacking teams, and in other teams there are better options probably. This counter shines in a setup where there are stealth rocks on the field and preferably a layer or two of spikes. That way the phazes are not only stopping qwilfish but punishing qwilfish for trying to abuse its turns of rain. It speeds the game up in a matchup where rain cannot outlast more than one or two rain dances with hazards up. Poliwrath has the dual utility in also countering kabutops, as well as omastar. Rest and sleep talk will keep it healthy throughout that match and just the presence of poliwrath really discourages water attacks, making the matchup that much better against rain.
tldr, poliwrath is a strong counter to qwilfish which finds its niche on hazard-stacking teams that need consistent rain answers.