I think I’d powerscale the Shichibukai like this:
Mihawk (Yonko level). Rival of Shanks and WSS, so Yonko level is reasonable.
Weevil (Admiral level). Alleged son of WB and compared in strength to a young WB. Should be Admiral level in order to be relevant at this point in the story.
Prime Moriah (YC1 level). Seemingly fought competitively with Kaido 25 years ago.
Hancock (YC1 level). Immediately got invited to the Shichibukai after just her first voyage, while a lot of the other people on this list took a lot longer to get recognized. Probably has ACoC since Marigold and Sandersonia have ACoA and ACoO, respectively.
Kuma (YC2 level). Portrayed as one of Dragon’s top 3 men alongside Sabo and Ivankov.
Post-TS Crocodile (YC2 level). Oda’s been wanking him nonstop ever since MF. Shown clashing with Doffy, hyped by Sengoku, wasn’t afraid of Akainu, was called a rival of Douglas Bullet, and is now credited, along with Mihawk, as justification for Buggy becoming a Yonko. Crocodile seems to have started his own crew/organization after MF, which we know nothing about but should probably be decently strong.
Doflamingo (YC3 level). Performed evenly or arguably worse than Cracker did against Luffy. Had to blackmail his way into the Warlords.
Jinbe (YC3 level)
I wish Oda would at least provide a reason why Crocodile was so much weaker in Alabasta instead of just magically making him stronger, but oh well
In the eyes of everyone, except a select few characters who actually know that Buggy’s weak, Buggy is basically just Shanks. A cabin boy from the Roger Pirates who went on to become a strong and fearless pirate captain that orchestrated the largest breakout of Impel Down, wasn’t afraid to fight WB (empty bluster that only his crew heard, but they spread the word afterwards), and wasn’t afraid to confront Shanks (friendly banter that people didn’t know the context about).
So yeah, the public thought that Buggy was basically a Shanks level fighter when deciding that his Cross Guild should be labelled as a Yonko crew. Of course, pathetic opportunists like
@ShishioIsBack don’t have the moral integrity to acknowledge this indisputable fact because it weakens their agenda.