Everybody who has ever been a warlord.
People such as Teach are ranked on the strength they had when they were Warlords. Not accounting for Croc or Teachs boost in power after their Warlord status was revoked ore renounced.
Teach, Law, Buggy, Mihawk, Hancock, Moriah, Croc, Jimbe, Weevil, Doffy, Kuma (Don't think I forgot any)
IMO it goes like this
Buggy and Mihawk are clearly Last and First but there are more varied opinions for the rest.