I'd say use common sense. Use your best judgment and try to use Pokemon that you actually see, regardless of UU or RU or NU status. Do you see Claydol used every once in a while? Not in this generation. Do you see Sandslash every once in a while? I'd say yes, along with Stoutland as they are very underrated sand abusers (especially the latter). And yes, the title may be a little misleading since I list exactly one set, but to make a thread about literally countering a Pokemon, it would be a much longer project.
I'm thinking we might start over. I'm glad this thread went so far without being too ridiculous; I hardly had to delete any posts, and iirc none of them were sets, just dumb comments. However, it's hard to "know" your opponent's set, especially something like Terrakion where something is likely to die no matter what it's using if you mispredict. That was the primary problem with the old "Counter that mon" threads.
My new vision for this project is to go in several stages.
Stage 1: Vote for a Pokemon to be countered.
Stage 2: Vote on a few sets (3?) for that Pokemon to use.
Stage 3: Decide on 3 Pokemon sets (they can be the same or different Pokemon) that are balanced enough to handle all 3 of the Pokemon to be countered's sets as well as function independently (basically, the ground rules of this thread).
I will post a template within the next two hours. Thank you for all who participated!