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!