Big Old Poster:
I'm too lazy to attach sprites, but I'll at least bold stuff.
New Drops:
Diancie => A
This is honestly the low end of where I'd but it, but there's no harm in erring on the side of caution. Basically, this thing is absurdly adaptable, being able to viably run a very usable Rocker set, which can go either defense, checking stuff like Incineroar and Sneasel easily, while still providing good enough offensive presence with its stabs and how great Diamond Storm is. The Calm Mind set, both in terms of Sub-Cm and 3 attacks is an absurdly scary breaker if you don't prep for it right, being able to OHKO Fairy resists like Steelix after one boost if they're running the low spdef spread, and just chipping them to deal if not. This is in addition to having good enough bulk to actually buy time to set up. Finally, its a good heal bell mon, and lets be honest, a good heal bell mon has been missing from the tier considering how toxic infested it is.
Gigalith => A
Another Rock type, another A rank: This thing is unbelievably fat, taking 52% max from Life orb Venusaur's Giga Drain, and providing a really solid defensive pivot and rocker, with great all around bulk. Being able to support Sand Sweepers like Stoutland and Sandslash is also insanely useful, with Stoutland having basically 0 opportunity cost when used with Gigalith as simply an offense destroyer. Not much to say other than that it works on Sand HO, and basically anywhere else with just it and 1 sand abuser.
Comfey => B/B-
This thing pairs impeccably with Probopass, and being able to both break stall while contributing against offense with that +3 Draining kiss is super useful. I've been using the Dkiss/Taunt/Synth/CM set that was popular in RU, and it just can end games if it isn't properly prepared for, or if the opponent uses Steelix as their main Fairy Resist. That said, I'd err to B- rather than B because Venusaur exists, as well as like every other Poison type, still good mon, and legit creates a really fun playstyle.
Ambipom => C/C-
So, Ambi's best use before rising was trapping delphox with Fake Out / Pursuit mind games; Delphox is dead now, and offense is often running Gigalith, which just laughs at it. Not seeing amazing reasons to use it, but hey, a strong fake out is still nice, as is stalling weather turns.
Old stuff:
Audino-Mega: A+=>A
Ok, so this thing is passive beyond almost anything else in the tier, requires you to have probably the best Venusaur answer ever, or give up either your way of beating half the stuff you're supposed to check or Toxic (aka your best attack), and honestly, doesn't love the fact that more and more hazards are popping up in the tier. Not 100% on this nom, but haven't felt it be as dominant as it once was.
Delphox: A=> A-/B+/Lower
So, this mon is real bad atm, as both Gigalith and Diancie laugh at it, while the newly invigorated Stoutland just trivially OHKOs it while outspeeding under sand. Legit, this mon doesn't really excel at much atm, and I don't really think it should be this high.
Type: Null: A+=> A
So, people are actually taking this into account, and many of its main targets in Delphox and Whimsicott have sorta fallen off, and Sand makes it even easier to pressure than before. Sorta iffy on this one, but its felt notably weaker than it used to, and A+ is real high ranked.
Stoutland: UR => A/A-
This thing is fast as fuck, strong as fuck, and punishes scald abuse with Facade, which it 100% has the moveslots to run. It completely manhandles almost every single offense variant, and with Gigalith being a very viable mon in its own right, the opportunity cost of running it has fallen to wayyyy lower than it used to be. Not much to say other than if you're running Gigalith its basically a hybrid Breaker/Revenge Killer, and wearing down Steelix isn't all that hard when you're doing 50% with Superpower every time you predict right, and 20% with return even if you mess up your prediction.
Sandslash: UR=> B+
So, fast as fuck, OHKOs Slowbro with a +2 Z-EQ, what more do you need, aside from the ability to not just die to every enemy Vanilluxe every time its brought out. Most people see Stoutland as the face of Sand Offense, but this is carrying so much of the playstyle, as it punishes so many of Stout's switchins, while posing a very competent offensive threat in its own right. Sure, its slow as all hell outside of sand, but in sand, its by far quick enough, and brings a lot of really scary stuff ot the playstyle. Only reason its lower than Stout is because its not as splashable, and doesn't fit on the kinda Sand Balance playstyle that's been popping up recently.
Vivillon: A=>A-
So, this thing doesn't love the more offensive tilt the meta is taking, as well as the fact that one of its sets, sub QD just got a fuck ton worse, as Stout outruns at +1, Gigalith/Diancie take approx 0 from anything not called energy ball (and even with eball, +1 252 SpA Vivillon Energy Ball vs. 252 HP / 252+ SpD Gigalith in Sand: 128-152 (34.2 - 40.6%)), basically making it so that you have a lot less ambiguity when facing it. This is not a major change, as Viv still puts in insane work vs a lot of non-sand squads, but the rise of Sand really didn't help its viability, even if it can still work there.
Xatu: A=A-/B+
So, like, is anyone not keeping Xatu in mind while building? Curse Lix can be run to just plow through it, you have to give up so much offense its not funny to not just die to Sneasel, making it arguably setup bait, and both of the new Rock type Rockers just bypass it by threatening to chunk it for like all its HP while taking almost nothing in return. The only meta trend that actually favors it is Ferroseed existing again, but that's IMO not enough to save it.
Altaria: B=>B-/C+
Holy crap is this mon passive, plus it loses to all the new rockers trivially, drop. Like, what does it even excel at anymore, aside from giving legit like half the tier's sweepers free setup.
Golbat:B-=>B+/A-
So, Venusaur is currently our god, and this is by far the best answer to it. It also has the ability to be easily customized to almost any team with a wide variety of supporting options in Super Fang, Toxic, U-turn, Taunt, and all its tech options, as well as being a fairly usable Defogger (even if I prefer Stallbreaker). All in all, a pretty solid mon, and provides a lot of defensive utility to a ton of teams, while not inviting in the most mons (Klinklang, Rock Type Rockers, but they get Fang'd, Electrics), which aren't impossible to build to beat.
Ferroseed: C+=> B-/B
So, another nom almost entirely because it beats Venusaur, but this time it also sets up spikes, as well as heavily taking advantage of the recent fall in Xatu usage. Beating Diancie 1v1 easily is also nice, as CM diancie can be a huge threat to Balance/Bo atm (barring Hp Fire), while also beating Klinklang, which is always a plus. Just generally pretty solid, sure it may invite in a few annoying sweepers; see Incineroar, but shutting down some of the tier's biggest threats without much worry is just really solid, as is spikestacking, which allows it to pretend its less passive than it is, by just threatening the opposing team.
Monster Post, and there def is more I could say, but anything more and I'll just start making worse arguments than I already am.