Asking because no one likes to answer, what is a consistent Kyurem check?
Glowking can take one hit from specs and is a freeze risk (don’t lie to yourself and say it’s a consistent switch in) and is set up fodder for every other set.
Gliscor has to burn Tera to force it out and even then can’t beat every set.
Zama can deal with it once with roar before getting too low.
Well, the main thing is you have to figure out if it is special or one of the DD variants. So it isn't one check, but at least 2 that you usually need. Some will say that skilled players can tell based on the team comp, but this is only partially true. Pinkacross even had a video where he had the same basic teams with different Kyurem sets at highladder and no one was able to guess the sets in time. But there are a couple tricks you can use.
First, hazards and sometimes team comp can tell you if they are boots or not. Boots sets are generally a bit less threatening. Rocks also limits the amount of times non-HDB Kyurem can come in. So it's useful for teams with any sort of offensive pressure or phasing.
Because the special sets have more immediate wallbreaking power, it is generally better to first assume they are special until you see the DD. So you switch in the special wall first, and then you go for the answer to the physical set.
However, this requires that you then have a proper switch into the DD sets at +1 or so. Another issue is the variance of DD sets, which could abuse Tera Blast, be mixed, or even a stalling set. Personally, it is the variance of the DD sets that pushes me over the edge with it. If the DD sets could be relied on to be purely physical damage, it would be a lot easier to counter this mon.
I find that forcing Kyurem out at least once is something you really need to be able to do. If you have phasing or force it out with offensive pressure, you can force a reteat after finding out a little information about what set it is. Then it is easier to deal with it. Like Roaring it out with Zama once can be enough if you know what it is.
As for things that counter every set, nothing really does. The closest thing I saw was AV Scizor with Mola Wish support. Iron Crown isn't a counter, but it can take an Ice move and threaten it back. Corv can sometimes be an answer, but because it is only neutral to Ice moves, it really depends a lot on the respective sets. There is also Bronzong, which can do that and a couple other handy things, but mostly is trash otherwise. Another very niche mon that I have been experimenting with Orthworm, but this needs more testing and, even if it turns out ok, may only be decent into DD variants.
In general, you want to look for Fire or Steel types that don't lose to Ground coverage. Most Water types don't cut it because of Freeze Dry and Ice types just aren't a good enough defensive typing. Most Thick Fat mons are too low tier for OU, have inconvenient typings, and/or rely on other abilities like Azu.