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DT/Thunder Kyogre as a Walrein tank counter?
Yes, it exists, but it is legacy and no one ever gets it.
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Of course, otherwise DT/Blizzard Kyogre would have completely annihilated Rayquaza. Sticking Kyogre with only a water fast move meant that it was not optimal against anything that resists water.
I suspect Niantic would never release the strongest possible pokemon (until primal Kyogre and Groudon, of course) right before the thing that it is a perfect counter for.