I think with Conk the problem comes from how matchup reliant it is as a wallbreaker. Its movepool is OK, but it always suffers from either being walled by something it needs to break or sacrificing a priority move (i.e. its way to outpace faster Pokémon) to hit all of its targets with its coverage options. If there were no Fairy-types to worry about, Conk would be significantly better at its role, but the fact that it has to choose between Mach Punch, Knock Off and Poison Jab means that it needs significant support to handle a lot of the things it needs to break. TBH, there are better choices for a team the majority of the time, and I fully support it moving down to B-. Additionally, like bludz said, it needs to sacrifice a significant amount of bulk to outpace walls such as Clefable and Heatran, to the point of one of its main selling points simply losing prominence. Unless a metagame shift which renders pokemon like Clefable obsolete (not going to happen), Conk's effectiveness is severely capped, with it being just barely B- material in the current state of the meta. If there are any metagame shifts that favor Fairy- or Flying-types, no matter how minor, Conk will tip over the edge into mediocrity, and it is something which needs to be kept in mind when discussing him as a Pokémon. It also makes one question why it hasn't dropped under the 3.41% usage bracket that defines OU while Pokémon which are actually good, such as Volcarona, Hippowdon, Alakazam, Pinsir and M-Aero, are stuck in BL and below.
Alright I'm going to have to disagree with a few things you said here.
Let's address your first point about Fairies and Clefable.
I'd like to bring your attention to this calc first: 252+ Atk Life Orb Sheer Force Conkeldurr Ice Punch vs. 252 HP / 160 Def Clefable: 172-203 (43.6 - 51.5%) -- 64.5% chance to 2HKO after Stealth Rock and Leftovers recovery
Even Bold max/max Clefs take up to 42%, and if they're Unaware and being affected by Rocks as a result that's already enough to pressure the Moonlight, giving the Conk user a free turn to switch out. Of course, this is also assuming Clef is absolutely healthy and can even take the second hit.
SF Conk isn't like AV Conk where it can't do damage to anything with respectable bulk without a Super Effective hit.
The center of your argument for moving Conk down seems to be the prevalence of Fairy types, yet it still does a hefty chunk to Clefable without even resorting to Poison Jab. But even if you ignore or dispute that, if you notice in my previous post on page 113 I list off a few of SF Conkeldurr's most ideal teammates.
Talonflame, Excadrill, Zard-X, Metagross. They all either murder or set up on the typical defensive Fairy type.
You say that Fairy types limit how Conkeldurr performs at its job but that's really not even true considering Conkeldurr's job is to mow down walls for
a bunch of teammates that all beat Clefable. Idek why you seem convinced that Pokemon X's existence obstructs Pokemon Y's ability to lure and break A,B and C, that logic is fallacious to begin with without even going into the rest of what I said.
Your second point is about
Conkeldurr's apparent 4MSS. Eh tbh SF Conk doesn't have it, at least, not any more than Pokemon like Metagross and Landorus. I put slashes in my set for the sake of flexibility but the best moveset for SF Conk in my opinion is always Superpower / Mach / Thunder / Ice. SF doesn't use Knock Off so idk why you even mentioned that, and Poison Jab is mostly not needed as I explained above. You can use Drain Punch over Superpower if you prefer the longevity but that's about it.
Then you say that
SF Conkeldurr sacrifices too much bulk. Even with absolutely no investment in bulk it still has natural bulk comparable to Garchomp, which is pretty good, and it's not like there aren't alternative spreads that can afford to invest in more bulk. My spread outspeeds Defensive Skarmory but if you're pairing it with Zard X and Skarm isn't a huge concern, you can run just enough for Clef and Base 60, which is only 128 Spe EVs, which leaves you at a rather beefy 383 HP if you invest the rest in HP. Conk never EVs for Heatran idk where you're getting that. I'm not denying that Conk loses significant special bulk without AV but I think you're overselling the significance of a few lost HP EVs that the AV set never even ran to begin with.
And lastly I won't even address the last section of your comment because it doesn't really hold any relevance in a viability thread. Despite how much it seems I'm praising Conkeldurr, we've already established that Volcarona and Alakazam are more viable than Conkeldurr right now, and I never disagreed with that or argued otherwise. I simply don't think we should be knocking Conkeldurr down even further when it
does have redeeming (and underrated) qualities that keep it on par with the likes of Crawdaunt, Hydreigon, and Amoonguss in
B.