-> A-
I think a lot of people underestimate the damage Dhelmise can do. While it seems to be outclassed by Decidueye on the forefront, as Decidueye has it's own exclusive z-move, has a bunch of sets, and even performs the role as a Swords Dance user better, Dhelmise has some things that it does better than Decidueye. For one, Dhelmise is a much better Choice Band user. It's Grass STAB is extremely powerful in Power Whip, which is pretty much doing damage to everything bar Poison-, Steel-, and Flying-types. For the Poison and Steel-types however, Dhelmise carries the move Earthquake, which does heavy damage to pretty much all the Poison and Steel-types. For those pesky Flying-types including Aerodactyl and Braviary, Dhelmise has the STAB Anchor Shot (which traps mind you). Now, this set as a whole has extremely few switch-ins. I'm sure there's more than I'm claiming, but off the top of my head the only one I can think of is Vileplume, which takes little damage from all of Dhelmise's attacks. However, Dhelmise also happens to have Knock Off, which can be run for the last move (there are other options such as Shadow Claw and Switcheroo as well). With this in mind, nothing really is escaping the wrath of Dhelmise, given that Dhelmise is in versus a slower / bulkier foe.
The main issue with Dhelmise is that it's rather slow. While it does pack some decent bulk, having 70/100/90, I do feel that Dhelmise can't really afford to take a hit, especially if it's running the Choice Band set (I'll mention some other sets later). Therefore, it can be hard to get Dhelmise in without forced switches and revenge killing. Another issue is that it's not a very good revenge killer, which limits even more of your options to get it in. Simply, it's just hard to get Dhelmise on the field to do damage in the first place, meaning it does require a bit of support to help it get in, such as pivoting moves from Rotom or Heliolisk, or by other means listed above. This is why Dhelmise isn't so high on the list as it might want to be.
Dhelmise has other sets as well, I suppose it could function as a Rapid Spinner but that isn't as good as it seems because you're kind of forced to be walled by something given that you kind of have to run Rapid Spin + Synthesis. So, realistically, you can only run Earthquake + Anchor Shot or Power Whip + Earthquake, while losing out on Knock Off, in my opinion, it's just not worth it. Some people could argue that you can drop Earthquake but with Incineroar everywhere and especially since it almost eats a banded Earthquake as it is, you're kind of required to run it. It also means that without it, you invite Garbodor in for free which means it will probably get up hazards given that you don't have a Xatu in the back, so it's really important that you have Earthquake.
Honestly I'm not too sure what else this has been running, the sets that I've mentioned are the only ones that I know about. One last thing I could talk about is that Anchor Shot kind of removes prediction on your side, giving you free switches and such, which can be a useful component. Also, this Pokemon hates getting revenge killed by the likes of Sneasel and Incineroar, which is something you should definitely keep in mind. Dhelmise can win 50/50s versus Sneasel, but it is kind of risky if you're a bit rusty on risk vs reward and such. Overall though, I think Dhelmise is an incredible Pokemon, and is only held back by it's Speed.
Here comes a nomination where I'm as informed lmao.
-> A/A+
So after talking a bit with some users about Decidueye, I've realized that I've been underrating Decidueye. I have not seen it in action that much, so I'm not sure how much my opinion matters here, but I think the versatility is incredible for Decidueye, as it already has like four good sets as it is. The most obvious one is Swords Dance. Now, you could argue that Incineroar just switches in for free, but another thing that you have to consider is that some users have been running Z-Low Sweep in order to do heavy damage to Incineroar. Otherwise, Ghost STAB is great, and hits pretty much everything bar the Dark-types and Normal-types, which are hit pretty hard by Leaf Blade. Decidueye, unlike Dhelmise, isn't too afraid of getting revenge killed. While Decidueye is technically not as bulky as Dhelmise, they're actually pretty close, with Decidueye having 78/75/100 bulk. But what really sets Decidueye apart from Dhelmise in this department is Swords Dance Decidueye being able to run Shadow Sneak / Sucker Punch. This allows Decidueye to at least get some chip damage versus Pokemon like Sneasel that might want to trap it and kill it off. Of course though, Shadow Sneak is mainly for those faster Pokemon that might be killed by it after some Stealth Rock / Spikes chip damage. It also is just great chip overall by itself.
As I briefly talked about in the previous paragraph, Decidueye does have some utility to help not get revenge killed. However, some of the better Pokemon right now, such as Sneasel and Incineroar, don't really care about the moves Shadow Sneak and Sucker Punch. While this is true, both Incineroar and Sneasel really fear Z-Low Sweep, so they can't really act as counters by any means. Sneasel on the other hand, actually works as a check, being able to get off super effective hits with it's STAB moves. Outside of Sneasel though, there's not much else. Personally, I am a fan of Physically Defensive Hariyama, which I know a lot of people don't like simply for the fact that Passimian and Hariyama can't be on the same team, and Passimian is on most teams right now. However, it can act as a check considering that Deciudeye has used up it's z-move. Hariyama can then Toxic + Protect stall it, while clicking Knock Off in between / on SDs. Vanilluxe and Braviary also check, as well as a few other Pokemon.
You may notice in the last paragraph that I talked about a few Pokemon as counters. That's because counters to Decidueye are actually extremely limited. While a lot of Pokemon check, not a lot of Pokemon want to come in on a Sinister Arrow Raid, or perhaps just a Spirit Shackle in general (which also happens to trap). There are also a lot of other sets that Decidueye can run that are really good, like that Defog set and a couple of others, although I don't feel comfortable talking about them since I haven't really seen enough of it.
So, all in all, I think Decidueye is a great Pokemon since between it's STABs and Low Sweep, it doesn't have a lot of switch ins at all. I apologize if this seems a little messy since, while I have seen Decidueye a lot, I haven't done any personal testing with it, so this may seem a bit uninformed, but I think my point still stands.
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These are pretty much the only two Pokemon I've really had any in-depth experience with, whether it be through testing or through watching others play. Some other nominations I agree with are
Sneasel to S, Aerodactyl to B+/A-, and
Quagsire somewhere in B.