New:
Komala
New! -> B First viable Rapid Spin user, and has a amazing ability and movepool, although it's stats leave much to be desired.
Qwilfish-H
New! -> B+ Great bulk with Eviolite, and an amazing utility movepool to make use of it.
Sliggoo-H
New! -> B+ New Steel-type with great bulk, abilities, and offensive coverage. Despite its coverage it can be quite weak though.
Sneasel-H
New! -> A+ Amazing offensive typing and stats, with bulk rivaling that of Toxicroak with an Eviolite. Choice item sets make great use of Sneasel-H's high BP STAB moves and Trailblaze SD sets let Sneasel sweep quite well.
Thwackey
New! -> B- Grassy Seed facilitates all kinds of different strategies, and Thwackey's natural bulk and access to Knock Off makes it a solid standalone Pokemon in its own right.
Rises:
Rotom
S- -> S Rotom has lost competition in Passimian as the best Choice Scarf user in the tier. Substitute + Nasty Plot sets destroy defensive teams and Rotom's virtually unblockable Volt Switch makes it a fantastic enabler of slower offensive threats like Clawitzer or Ursaring.
Scyther
A+ -> S Scyther is the premier offensive pivot of the tier, forcing out switches with its powerful STAB moves and coverage to either Defog, pivot out safely, or get a Swords Dance to sweep. Trailblaze sets have been dominating in NUPL as Scyther very effectively breaks for itself by weakening its few checks with U-turn. Scyther also provides a Ground immunity and Fighting resist on top of the aforementioned Defog, making it extremely difficult to justify NOT putting on any team.
Cacturne
A -> A+ Cacturne's offensive prowess paired with a surprisingly solid defensive profile allows it to break giant holes in teams while laying down Spikes for itself and its allies. Spiky Shield allows Cacturne to scout and punish U-turn from Scyther, and Cacturne has a positive matchup against Rotom while greatly benefitting from Passimian and Zoroark's departure.
Dudunsparce
A+ -> S- Dudunsparce's raw bulk is unmatched, which makes it an incredibly fearsome setup sweeper on both the physical and special side. It's been dominating in NUPL as well and has very limited counterplay depending on its sets.
Jolteon
A -> A+ Jolteon's uncontested speed tier and perfect coverage found through Tera Ice makes it a super scary sweeper late-game and an amazing pivot leading up to that. The Volt immunity and serviceable special bulk lets it pivot into Rotom and Eelektross relatively safely.
Ursaring
A -> A+ Ursaring's Guts set is an absolute beast that bypasses all physical walls like Sandaconda and Qwilfish with its raw power alone. It can even use Trailblaze to sweep slower teams lategame, but with all the pivots available to us currently, Ursaring is a fearsome wallbreaker. Eviolite sets have also seen lots of use, even 2 attacks without Bulk Up, just serving as a solid tank, some teams just simply can't safely take out Ursaring without getting lucky with Sleep Talk rolls.
Magneton
A- -> A Choice Specs sets are nearly impossible to switch into, Tera Flash Cannon OHKO's Sandaconda WITHOUT Analytic. Most special walls lack recovery like Muk and Eelektross, allowing Magneton to wear them down with Volt Switch and bring in something better suited for the job. Eviolite sets make use of Magneton's solid bulk and Steel typing to be a great offensive pivot.
Oricorio-F
A- -> A Oricorio-F, much like it's cousins, has access to broken Quiver Dance and makes excellent use of Tera to turn the tables on traditional checks. Tera Ground to snipe Muk and Grass to beat Vaporeon, Oricorio is a very potent sweeper with lots of set variety.
Bombirdier
B+ -> A+ Although it appreciated a positive matchup against Zoroark, Bombirdier's utility is way too good to be anything lower than A+ currently. It was only a matter of time before people figured out how to utilize such a customizable Pokemon and its currently one of the best defensive pivots, with access to the limited Knock Off and being a Stealth Rock setter not named Sandaconda.
Indeedee-F
B+ -> A- Indeedee-F is a very powerful special breaker, capable of beating its checks through coverage or Trick, and also boasting Healing Wish as a utility option. Indeedee's speed tier is quite nice for how powerful it is.
Pyroar
B+ -> A- Pyroar's speed tier and power makes it an amazing wallbreaker, with access to Taunt and Will-O-Wisp to shut down defensive answers like Umbreon. Pyroar's defensive profile is also quite nice, resisting U-turn and immune to Ghost.
Braviary
B- -> B Braviary is a scary setup sweeper with Bulk Up and Tera to provide a free setup opportunity, but physical defensive sets can check Scyther quite nicely and offer Defog and U-turn support as well. Tera Ground has been used to setup on Electric-types like Rotom and Eelektross.
Glaceon
B- -> B Access to Freeze Dry and Ground coverage with Tera Blast makes Glaceon near impossible to switch into. Calm Mind and Choice Specs sets are both great wallbreakers.
Sawsbuck
B- -> B Sawsbuck's typing gives it an advantage against top tiers like Sandaconda and Rotom, allowing it to set up and take advantage of Serene Grace Headbutt.
Camerupt
C+ -> B- Camerupt can stop Rotom's Volt Switch and threaten it back while setting up Stealth Rocks.
Lilligant
C -> B+ Lilligant has broken Quiver Dance and great coverage with Pollen Puff and Tera Blast, making it an incredibly threatening setup sweeper. It also has solid utility options in Sleep Powder and Healing Wish.
Raichu
C+ -> B- Electric immunity with Nasty Plot and a bevy of coverage options available makes Raichu a solid sweeper. Raichu has commonly made use of Tera Draining Kiss.
Leafeon
UR -> B- Trailblaze sets have been seen on HO teams with Swords Dance to complement Leafeon's great offensive stats, utilizing Fire Tera Blast for great coverage.
Swalot
UR -> B- Swalot offers very similar traits to Muk, but has Encore and Earthquake at its disposal with better physical bulk as well.
Dugtrio
UR -> C Fast and has Stealth Rocks I guess
Muk
S- -> A+ Muk's initial rise was largely due to its ability blanket check most of the tiers special set up mons with Haze and a reliable Scarf Rotom switch-in since Sticky Hold prevents Trick. However, as the meta has developed, we've seen more structures built to chip away at Muk making it unable to properly stop setup. Additionally, the meta has started to drift from Scarf Rotom to more utility sets with Will-o-Wisp.
Umbreon
A+ -> A While still a great defensive pokemon, its passivity makes it giant momentum suck on your team, making it hard to fit on many teams.
Vaporeon
A+ -> A Similar to Umbreon, the passivity of Vaporeon is difficult to avoid. Grass-types have been increasing in importance on teams and this does not bode well for Vaporeon.
Lurantis
A -> A- Lurantis faces steep competition as a team's Grass-type from Appletun and Cacturne. The trouble Lurantis finds itself in is that it often requires Tera to threaten common switch-ins. It's also quite linear, and has very little versatility comparatively to Appletun and Cacturne.
Mabosstiff
A- -> B+ There are Pokemon that can match Stakeout's power without needing to reach the requirement that Stakeout has; you can simply just not switch against Mabosstiff and it becomes quite bad.
Perrserker
B+ -> B Despite the Steel typing, Perrserker's bulk is still terrible.
Rotom-Fan
B- -> C Virtually useless ability, and Air Slash is just a bad STAB move. Also large opportunity cost for not just using regular Rotom.
Vespiquen
B- -> C+ Incredibly passive and weak to common types in the tier.
Whiscash
B- -> C+ Beyond setting hazards, Whiscash's stats and movepool just leave a lot to be desires.
Zangoose
B- -> C+ Thoroughly outclassed by Ursaring as a Normal-type breaker, often faints before even getting to take more than one KO.
Basculin
C+ -> C Thoroughly outclassed by Bruxish as a Water-type breaker, often faints before even getting to take more than one KO.
Flapple
C+ -> UR Thoroughly outclassed by anything as a any-type breaker, often faints before even getting to take more than one KO.
Squawkabilly
C+ -> UR Outclassed in every way as a Guts breaker, has to kill itself to do any meaningful damage.