My personal opinion, since I haven't personally tested some of these pokemon, my primary evaluation strategy was to determine the most centralizing pokemon and evaluate the rest of the tier based on their viability against them (as you can see, dark types tend to do well, since there is a multitude of very good ghosts and psychics):
--Ordered within tiers--
S
:Gourgeist-Large: All Hail King Gourg
A+

Gothitelle: pretty strong wincon with few real checks

Dusclops: special wall resttalker and pseudo-offensive spinblocker
A

Linoone-Galar: Best Dark in the tier, mandatory A, very versatile

Mr. Mime: the underrated, actually more effective Mime

Machoke: Very good stallbreaker, unfortunate speed tier

Oranguru: Ghost immunity, amazing coverage

Silvally-Ice: versatile, one of the best physical sweepers, great special movepool

Mr. Mime-Galar: Overrated Mime
A-

Vullaby: Dark type, offensive Gourg check, hazard remover

Morgrem: np, super useful dual STAB, priority status user

Persian: worse Linoone-G except for Fake Out, which is one of the best moves in the tier

Pyukumuku.

Klang: Good typing, solid resttalker

Farfetch'd: Very versatile, fantastic priority, slow + frail and weak to rocks

Corsola: Very solid longevity = very solid rocker, also a physical chipper

Ivysaur: Knock off + recovery + beats most stall pokemon

Cufant: Steel + solid offensive prowess + rocks
B+

Gloom: bulkier ivysaur without knock off

Trubbish: only relevant tspiker, can also use spikes

Krokorok: Pressures psychics and ghosts and can set rocks, frail

Shiinotic: Gloom with worse typing and better statusing

Octillery: Amazing Stallbreaker, slow and HATES chip damage

Rufflet: Glass cannon: band/scarf, amazing but frail stallbreaker

Lampent: trick user, very useful STAB

Seadra: best offensive water due to good speed tier, decent SpA, and easy switch out potential

Natu: Magic Bounce
--In a much more relative order--
B

Eiscue

Wartortle

Whiscash

Sudowoodo

Torracat

Duosion

Dartrix

Lickitung

Zweilous

Solrock

Hippopotas

Charjabug

Beartic

Lunatone

Glalie

Hakamo-o

Frillish

Mudbray

Dwebble

Stunky
B-

Spritzee

Palpitoad

Onix

Tentacool

Shedinja

Maractus

Drakloak

Gastly

Bronzor

Swirlix

Jigglypuff

Porygon
C
Basically everything else, feel free to let me know if I forgot anything!