Got some hot takes to drop.
A- -> B+
This might be just a hair controversial, but I think Rhydon is starting to falter. I've noticed that it's becoming less common on the ladder, especially when Alolan Muk started to run Sassy for it (Mega Drain) and Melmetal (Fire Blast) not too long ago. It has forced some users to start running Jolly natures on their Rhydon to keep up with it, which affects various rolls such as Rock Slide vs Lead Aero having a small chance to miss out on the OHKO. Not only that, people are preferring to use faster Stealth Rock setters that offer much more utility like (Mega) Aerodactyl, Alolan Dugtrio, and Nidoqueen than the "very first Pokemon". I think Nidoqueen in particular, a fellow A- mon that's the most comparable, is just better than Rhydon in this meta overall. It has a Toxic-immunity which is such a boon to have in this meta, it has a faster Speed-stat which lets it outpace everything up to Eevee-Starter when Jolly is used, Super Fang is just so good at chunking everything that comes in on it, and while this is a somewhat minuscule point, you actually resist U-turn from Zapdos meaning you take 3% less damage from each use of it, and the extra damage that Rhydon takes from it, plus its vulnerability to Toxic, actually adds up quicker than you'd think, and it honestly makes it a much weaker Zapdos switch-in than Nidoqueen and even Alolan Dugtrio. Hell, even Zard X has started to use special variants that totally mess up Rhydon on the switch. Fire Blast on the switchin + Dragon Pulse = a dead Rhydon.
As for the rest of the mons in A-, I strongly believe that they're all more viable in the current meta than Rhydon is right now, especially Mega Venusaur (this thing is so annoying af to face, I swear). Rhydon just simply doesn't fit in that ranking anymore and, in my opinion, B+ suits it better. With all the roasting I just gave to Rhydon, it's still not a bad Pokemon at all, but it's not A-rank material like it was a week ago.
Speaking of Eevee-Starter...
A+ -> A-
This thing is also a tad overrated, if you ask me. Like Rhydon, I've been seeing this mon less and less, too. It's too slow and too frail for it to come in vs anything, and while it can be annoying for teams to face thanks to its signature moves, it finds itself in a somewhat awkward position now that the meta has started to become much faster. As someone said here earlier, it's lucky if it's able to get more than one of its support moves off before it gets severely chunked by something. That being said, the utility this mon brings is unparalleled which is why I still think it deserves A-, but it just doesn't have the stat distribution to succeed as much as it'd like to.
B+ to A- maybe even higher
Then, there's Mega Gengar. B+ simply doesn't do this mon enough justice. I personally don't even think A- would do it enough justice, but one step at a time. This thing is a menace right now thanks to Protect + Disable messing everything up from Alolan-Muk to Zapdos. The mind games that this set has created in LGPE OU cannot be ignored. A-Muks have started to use Fire Blast turn 1 vs them more often to avoid the Crunch Disable, which only does like 27 max if Gengar decides to predict that and use Thunderbolt to start whittling Muk down earlier. It has much better coverage with access to Thunderbolt, which lets it hit Mega Gyarados and Alolan-Muk harder than Mega Alakazam can to both with Dazzling Gleam. STAB Shadow Ball is also, in my opinion, much more threatening than Zam's STAB Psychic and non-STAB Shadow Ball, where one Shadow Ball is a 2HKO on Melmetal after rocks, and the other is a 3HKO.
Mega Gengar absolutely needs to rise. Everything else in B+ is a joke compared to it, and even some A- mons like Starmie, Regular Zam, and especially Rhydon, aren't as good as Mega Gengar, at least in my opinion.
