Most insane captain? That would be Matt Decker, Ransom, Tracey, Maxwell, or Garth of Izar
Worst captain? Of the regulars, I'd say Archer. The guy had no leadership experience, and he screwed up so many first contact situations.
Guest characters, I'd say John Harriman.
Jellico was an asshole, but he wasn't a bad captain. The crew were just unused to an impersonal, subordinate>>superior style of command.