The meat of this post is gonna be on the controversial kitten bc I haven't seen much comprehensive discussion on it and would like to see a little more.
Sylveon A+ -> S: This is one I've been thinking about for a while and I just can't see it yet. Sylveon's a menace for sure; it's difficult to break and no slouch offensively - but there's a significant amount holding it back..
-4MSS. Not as much of a problem on Specs sets because it gets like, 2 coverage moves, but on cleric sets this is a nightmare. It needs Hyper Voice, Wish and Protect, so you're immediately down to 1 slot. In that slot, it wants one of Mystical Fire, Heal Bell and Calm Mind, all of which helps its matchups vs various different teams but leave it highly vulnerable to others; for example, without Mystical Fire it's fodder for the ever-common Roserade and the trending Escavalier, without Heal Bell it can't sit on fat mons like it would otherwise try to, and without Calm Mind it can struggle to actually get much breaking done - it's strong for a defensive mon but still not really that powerful.
-Stuff it'd check is already running stuff to answer it. Rhyperior and Gigalith used to sometimes run Heavy Slam for Weezing as a matchup thing, but now it's pretty much standard to deal with the kitty.
-While nothing in the tier can really do what cleric Sylveon does, its offensive sets face
direct competition from the very powerful Gardevoir. Between its stronger Psychic/shock, slightly stronger coverage moves and fairly comparable power with Moonblast, it's got a little more strength behind it. On top of that, it's faster, has utility options in Knock Off, Healing Wish, hell even stuff like Will-o and most notably Trick, and it has defensive utility in Trace allowing it to switch into stuff like Vaporeon and Milotic a little easier. It's not as bulky, sure, but offensive Sylveon really can't come in on much either. Plus, Scarf Gardevoir is a thing too - Sylv just can't pull off a similar set.
-It's just really quickly worn down. It suffers from one of its best answers, Roserade, being one of the two Spikers in the tier, which screws it over next time it comes in, in addition to the fact that the new defogger on the block, Rotom-Wash (which btw is a great pairing for sylveon) also hates it. It also takes sand chip, possibly toxic damage and is vulnerable to getting its Leftovers knocked off. It's all well and good that Sylveon checks Haxorus at 95% but it's just realistically hard to keep its HP that high without a lot of support - something that an S rank mon generally doesn't need.
Sylveon's amazing. It's threatening in every sense of the word and has a whole host of great traits that make it great against the current meta. But, in my opinion, it's just not S rank. Not yet.
---------------------------
Ok the rest of this will not be as fleshed out but here goes:
Gigalith A -> A+ - As long as sun's in the tier I definitely agree with this one. Being the ONLY consistent sun answer is huge, in addition to the whole host of other threats it walls. I think it's absolutely on par with the A+ mons - at the very least it's leagues ahead of all the A mons save maybe Incineroar.
Milotic A -> A- - No. It faces a lot of competition in Rotom-Wash now, but nothing is capable of sitting on half the tier like Milo is. It's such a threat vs bulky offensive teams and those are absolutely the most prevalent teams in the current metagame - if anything it's gotten better because it's a decent check to Darm and the loss of Mamo is huge because it couldn't take that on even tho it was supposed to. I think it's still a league above Mantine and the rankings should reflect that.
Reuniclus A -> A- - Team player cat is team player cat. Plus, there's so much offensive shit flying around like Roserade and Darmanitan that Reuni wants to check and just can't. It's not even that good of a breaker, either; Psychic might have great neutral coverage in this tier, but it hits like nothing SE. All of its sets suffer against something that's prevalent in the meta. It was overhyped to begin with and A- is exactly where it belongs.
Rotom-C A- -> B+ - Too much competition, too many things that wall it, not rly the best. I think it's got a lot of merit in the sense that it checks most of the other elecs but it's not a very good one on its own. I'd be fine w/ this.
Umbreon A- -> B+ - ;-; sorry esta but kitten is broken and it's just not good in fairy + coba meta. Umb's struggled for a while, I don't have much to say. It's gotta go down a little.
Flygon B+ -> A- - FIRE ASS FLYGON OML. Flygon's got so much to love rn; being one of the only Rock resists in the tier that isn't literally a Rock type, being the best Haxorus revenge killer ever, being great vs Sun, a solid Noivern revenge killer and more. It's got decent defensive utility alongside its ok bulk and is just so much better than its B+ placement says. Definitely should be a bit higher.
Passimian B- -> B - I have not used the monkey but my UUPL team has and it has put in work. It abuses the shit out of broken cat too. B seems fine.
---------------------------
And now for some personal noms:
Heliolisk A- -> A - Helio abuses the shit out of so many mons in this tier that it's kinda insane. It bops non-scarf Darm, walls Rotom-Wash, outspeeds and does massive damage to Cobalion, gets the freest volts ever on Doublade and Incin, laughs at every Water type in the tier other than like Pod, beats every Ground ever, is hard to switch into and is just so much better than literally anything at generating offensive momentum. It's fast, powerful and has real defensive utility despite its crappy bulk. What really sets it apart for me, though, is how much it abuses current teams - with the exception of Togedemaru (or Flygon if you're crazy), nothing can block its Volt Switch and get away with it, and in a tier with a million and one crazy breakers it's amazing to have a mon that can reliably get them in for free while still doing some damage. It's a cut above all the other elecs, minus Rotom-Wash. Being in A would reflect that so much more than its current placement.
Ribombee B- -> B/B+ - I've been preaching the bee for as long as I can remember now, but I'm finally making a formal post about it. Specs Ribombee is a massive threat that easily abuses this tier's severe lack of Fairy resists while being significantly faster than Gardevoir and Sylveon, its direct competition. It also has access to Trick to cripple opposing Sylveon which is huge for a lot of teams. In addition to its genuinely scary strength, it has access to Sticky Web, which is viable on Choiced sets and creates a playstyle that's incredibly difficult for most teams to handle that I've called "Semi Webs" bc I'm bad at naming things. A strong offensive partner - for example, Lucario or Choice Band Darmanitan - can take advantage not only of the switches Ribombee forces into mons like Escavalier and Bronzong (uturn's good!) but also abuses the shit out of the webs it can put up.
This is a team featuring -three- Choice Specs users that showcases not only Specs Ribombee's breaking power but also its ability to support more breakers on its team. I think this is incredibly unexplored and Bee's rank seems to be based purely off its sash lead set, which is upsetting. Hopefully this one gets considered.
I've been writing for like half an hour so I'm gonna stop but expect a post on some mons like Linoone and Haxorus in the future. Thank you for reading and remember to stay safe and wash your hands in these trying times.