If the grimoires I’ve seen are anything to go by, Hell is either a monarchy or an empire (nine or ten kings—Bael, Paimon, Purson, Balam, Viné, Belial, Asmoday, Beleth, Zagan, and possibly Decarabia—but I’m guessing Lucifer is an emperor). Democracy as we know it is actually a pretty new conceit (not counting anarchic societies like some Pacific Northwest indigenous had).