Corporal Levi
ninjadog of the decade
I agree with most of these, but a few that I'm less inclined to support are Cottonee's, Ponyta's, and Porygon's. Also not too sure about Chinchou/Croagunk at this pointFirst of all I'll talk about Scraggy. LOL if you think that's S you need to reconsider Fletchling's existence, Spritzee's existence, Mienfoo's existence, and Dazzling Gleam's existence. It got stealth nerfed as fuck this generation and there's a reason it's low. I would barely consider it an A Pokemon.
Bunnelby is one-dimensional and can't take one hit. It doesn't have a super reliable way to remove Misdreavus and as a Scarfer lacks the power to deal with the bulky Fighting-types. Stay B.
Ferroseed is really good but it can't do it's job without some major support and checking capabilities because it's set up bait..... and it can't do "everything" at once; it even needs support supporting. Stay B.
Prem asked me to make a post about this thread which I've been putting off since bans and stuff and also there's so much shit.
A -> S
Chinchou's an S Pokemon even if it doesn't resemble the power of Misdreavus or Pawniard. It fits on literally every team. It checks like every Pokemon, can spread paralysis or heal bell. If your team is missing something, you should probably add Chinchou to it.
A -> B
Croagunk is really cool and useful at times but it's not even close to A rank. It is weak and frail in comparison to the attacks it will be required to take. If it was faster, stronger, or bulkier it could easily abuse it's awesome typing, but currently all it has is the typing, ability and movepool.
Cottonee is obviously a niche Pokemon. It's very useful but it can't be that useful. Pure support doesn't have enough moveslots for Substitute, Tailwind, Encore, Leech Seed, Memento, Taunt and Knock Off while the attacking variant has room for one less. Use it to set up Zigzagoon etc but it's otherwise not super threatening.
Ponyta is weak to Stealth Rock and can't even think about getting passed Chinchou. It's not bulky enough to take a bunch of attacks after Stealth Rock even if it makes a decent switch into Mienfoo the first time, the second and third will be harder to do without Eviolite.
Porygon is still strong, but the omnipresent Fighting-types literally destroy this former powerhouse. It still has uses for checking Fletchling and etc but otherwise it's not good enough to warrant giving Mienfoo / Timburr / Scraggy a switch-in.
Vullaby I have literally no fucking idea how this got here. It's a defogger that's slower than the most common Stealth Rockers and loses to them handily. It still has its uses and can function effectively on some teams but B rank is even pushing it.
B -> A
Trubbish has stormed the LC metagame with Meditite's removal. It can switch into Mienfoo and lol at basically every move. Pawniard even has trouble with it. It can be set up bait for Missy, that's true, but it can also Spike and switch out. It's really useful and I'm sure we're going to see it even more, possibly even with Dark Pulse.
B -> C
Staryu kinda sucks now :(. It can't beat Misdreavus even if it switches into Hydro Pump. It is simply outclassed by Taunt and Defog. It doesn't have Chinchou's electric-typing and immunity which is what carries that so far, and it isn't bulky enough to take advantage of recover.
C -> B
Zigzagoon is a real threat this metagame. Berry Juice and Knock Off buff made Eviolite slightly less plausible to maintain and abuse, meaning almost everything is OHKOed by ExtremeSpeed. It still needs some Memento and Pursuit support though.
Onix is simply B because it can Taunt fucker Dwebbles and set up its own SR. Meditite no longer exists to punish Onix either.
I could get even nitpickier with Geodude -> C but I'm kind of tired already.
Corkscrew pretty much covers my thoughts for Cottonee and Porygon. Although Cottonee can't do everything at once, it can still do what it chooses to do very well thanks to a combination of its typing and movepool, while being able to check what is currently the most popular Pokemon so well grants Porygon a solid niche.
Ponyta does not completely lose to Chinchou; iirc Corkscrew has a Sunnybeam set on his Ponyta analysis, which I have seen others use and myself have used with good results; with such a set, Ponyta ends up beating Chinchou more often than not. Even with Stealth Rock in play, Ponyta is able to switch into Pawniard in particular and mash Morning Sun until the 30% burn chance kicks in. 120 base power fire-type moves are also nice when backed by something that hits 19 speed, so it's not like Ponyta's a dead weight offensively.