Sliding Scale of Villain Threat

An antagonist can be classed on three orthogonal parameters:
 * How much danger they, or their plans, pose.
 * How effective they are.
 * How much the audience is supposed to hate them.

This is a method of quantifying the first one.

Superman is locked in a battle with Lex Luthor, who is threatening to melt the polar icecaps and flood the world. Meanwhile, in Gotham, the Joker is going to gas the city and meanwhile in space, the Green Lantern is getting ready to defend against the invading Sinestro Corps. All of these examples have villains that are exhibiting differing levels of threat.

You can class various villains on tiers of the type of threat they present to the world and the heroes. The Sorting Algorithm of Evil will usually ensure that the hero's successive opponents will each be higher on the scale than the last, but, due to the SAoE's caring about effectiveness as well as scope, not always. In general, the hero will also have the same potential for destruction as his villains, but usually is slightly below them, because underdogs are more relatable. Having a wild range of villains may help avoid causing a feeling that The World Is Always Doomed because Evil Only Has to Win Once. Having a hero with a Story-Breaker Power usually upsets this dynamic, or forces a jump in villain up the scale.

Most series that lean towards the realistic side of the scale do not venture beyond Planetary Threat level, as Galactic and above tends to put a lot of pressure on Willing Suspension of Disbelief. Shifting too far up the scale, especially over a short period of time, is an easy way to Jump the Shark.

When talking about some villains, this is very much related to how much they can abuse the Kardashev Scale for death and maiming. Contrast with Sliding Scale of Antagonist Vileness, when you're talking about the audience's reaction to a character rather than the threat they represent, and Sliding Scale of Villain Effectiveness when talking about how well they succeed.


 * Personal Threat: The villain poses significant harm to a single person or small group of persons.
 * Examples: most serial killers from slasher movies, any normal person severely pissed off, most comic book Bad Ass Normals, the average vampire who doesn't refrain from drinking human blood, Dr. Facilier and the more mundane Disney villains such as Cruella de Vil and Gaston and the not so mundane but violently petty ones like the Queen and Maleficent, 24's first-season villains (Ira Gaines, the Drazens. Then again, killing David Palmer could trigger significant civil unrest), Joe Chill, Catwoman, Toyman, the Riddler, Mad Hatter, Deadshot, Penguin, Man-Bat, Black Mask, The Diesels and Spencer, the Zed Stacks, the Pirates, and Johnny Cuba, Chameleon, Electro, Bullseye, the Scorpion, the Kingpin, the Vulture, the Green Goblin, GLaDOS, the Wizard of Yendor, the various Terminators, the Linear Guild, the Trio, Holtz, Spike, The XPs, Most villains from the first season of Bleach, Thrax and  from Animorphs.


 * City Threat: Villain possesses capabilities to do significant damage to or destroy a city.
 * Examples: a typical Non-Malicious Monster (mitigated by the fact that, unless hungry, will never strike first and their True Neutral alignment, but increased due to their raw destructive power and being hard to kill), The Joker, Scarecrow, Mr. Freeze, Poison Ivy, Captain Cold, Demona, Doctor Light, Parasite, the Fearsome Five, Doctor Octopus, Baron Blood, Deathstroke the Terminator, Rita Repulsa, some of Captain Planet's rogues' gallery, most Powerpuff Girls villains, Team Rocket, the alien ship from Sim City, and bad guys from Sin City could also count for that matter, Dr. Robotnik/Eggman (although sometimes a Planetary Threat as well), Syed Ali, Vladimir Bierko, Samir, the Los Angeles branch of Wolfram & Hart, most Touhou "villains", the Enclave, the Disney version of Frollo, and The Others and Martin Keamy's mercenaries.


 * State/Province Threat: Villain can wreak enough damage to destroy or otherwise defeat a large group of cities.
 * Examples: the Brotherhood of Evil Mutants, some of 24's Big Bads (Stephen Saunders, Habib Marwan, Abu Fayed, Jonas Hodges), the Defias Brotherhood, Prometheus, The Evil Hybrids.


 * National Threat: Villain can destroy a country or take it over and turn it into a Crapsack World. The path to Diabolical Mastermind tends to end here, but not always.
 * Examples: Lex Luthor, Black Adam, Devimon and Etemon, Morgan le Fay, Shendu and his Demon brethren, Gorilla Grodd, the Mandarin, Bowser, Ganondorf, King K. Rool, Phobos, Godzilla and most other Kaiju, Kotomine Kirei in the Fate route, the Sennites, many Disney villains such as Jafar, Professor Ratigan, Ursula, Scar, Shan Yu, the Horde and the Alliance in each others' eyes, often other countries in both fiction and real life.


 * Global Threat: Villain poses significant threat to the world at large, up to and including World Domination and/or Earthshattering Kaboom. In worst case scenario, is an Omnicidal Maniac. Usually via large army, colossal superpowers, or a Doomsday Device. Evil Overlord tends to describe them. An Ultimate Evil or a fictional Emperor is likely to be portrayed as a villain of at least this threat level. At this point you should start checking out Apocalypse How.
 * Examples: Vandal Savage, Amazo, Brainiac, Doctor Destiny, General Zod, Doomsday, Bizarro, Ra's al Ghul, Achilles de Flandres, Syndrome, Myotismon and the Dark Masters, The Red Ribbon Army and Piccolo Daimao, Sasuke and Orochimaru, Majora's Mask, Darkrai, Doctor Doom, Apocalypse, Kang the Conqueror, Ultron, Red Skull, the Homunculi, the Millennium Earl, Loki, Morgoth and Sauron, the Cybermen, Mother Brain, Ridley and the Space Pirates, the Black Hole army, Giygas, most major Nasuverse villains, Lavos, Red Falcon, the Doctor, Team Aqua and Team Magma, most Final Fantasy villains, the Gyaos in the 90s Gamera trilogy, Trudy and, Utsuho, possibly Flandre Scarlet, Kotomine Kirei in the Heaven's Feel route, Gilgamesh in Unlimited Blade Works, SEELE, Xykon and the Snarl, Cthulhu, the Brotherhood of Nod and the Scrin, the Fallen Lords, most of the Big Bads of Buffy the Vampire Slayer, Jasmine, Dark Danny (albeit only implied), SHODAN, Satan in Christianity and Islam, the D-Reaper, the Man in Black, the Deathlords, Weil, Omega, the Guardians (combination of fighting skill and massive army at their command), humans in general, and sometimes major world powers (such as the Axis Powers, the Soviet Union (during the Cold War), the Fire Nation, Adam Monroe, the Twilight's Hammer, Nightmare Moon, Visser Three from Animorphs, and Doctor Robotnik.


 * Multi-Planetary Threat: Forces able to credibly threaten more than one planet or solar system but probably not able to dominate a galaxy. Galactic Conqueror starts here.
 * Examples: all major races in Star Trek (Borg, Dominion, Klingons, Romulans, UFP, etc), The Saiyans and the Ginyu Force, the younger races in Babylon Five, the Cylons, the Combine, the Zerg, Ka Anor, the People's Republic of Haven, the Ur-Quan Kzer-Za and Kohr-Ah, the Tau Empire and the ancient Eldar and Dark Eldar (Eldar because they have ulterior motives, and Dark Eldar because they are far too busy getting off on their torture of prisoners to have higher goals) from Warhammer 40 K, the Phfor Empire and Notorious Mental, The Successor States, the Clans and the Word of Blake, Grand Admiral Thrawn and the other post-Palpatine Imperial warlords of the Star Wars Expanded Universe usually blurred the line between this and Galactic Threat: their ambition was usually galactic, but aside from Isard, Thrawn and the Emperor Reborn they rarely had a credible chance of reconquering the galaxy, the Yevetha, the Mandalorian Neo-Crusaders and most other non-Sith antagonists in the Star Wars EU also fall somewhere in this category.


 * Galactic Threat: The Villain has the capability to destroy or control the best part of the galaxy. Galactic Conquerors are this threat level.
 * Examples: Emperor Palpatine, most other Sith Lords, the Yuuzhan Vong, The Borg (again), Species 8472, First Ones, Despero, the Fremen, the Skrull Empire, Sinestro, Parallax, most of the non-Heartless Kingdom Hearts villains (sort of), Purge, the Sailor Moon villains, Frieza and Cell, the Dalek Empire, Trigon the Terrible, any major villain group in the Stargate Verse, the Bacterions, the Reapers, the Decepticons, the Highbreed and the DN Aliens, the Governance de Magi, Andross, several races from Warhammer 40000 (the Necrons, the Tyranids, the unending tides of Chaos, the Orks, and, hell, the Imperium of Man itself), King Ghidorah (Showa version), the Blight, the Excession, the Empire, Foundation, Second Foundation, Gaia, Boskone, the W'rkncacnter (low-level estimate), The Covenant, the Solarian League and the Mesan Alignment (at least for the known galaxy from humanity's point of view).


 * Universal Threat: Villain can conquer the universe, or even cause The End of the World As We Know It - all of creation blinked out or ground beneath an iron boot. Dimension Lords are this threat level.
 * Examples: many Eldritch Abominations, Mr. Mxyzptlk, Darkseid, Glory, Galactus, Thanos when in possesion of the Infinity Gauntlet, Majin Buu, Baby and Omega Shenron, Apocalymon and Millenniumon, Exdeath, Nerissa, United Alliance of Evil, The Master, the Ten Wise Men/Luther, the Anti-Spiral Collective, (only at this level because it is uninterested in other realities) Bowser in Super Mario Galaxy, the Xeelee and Photino birds, The Flood, The Zerg (again), Deathborn, Cyrus, from Kid Radd, the Krikkits, U-DO, the Gnosis, the planet Meteo, potentially Alma Wade if she gets around to it,   from Everworld, Haruhi Suzumiya if she ever finds out about her powers, Azrael, Yawgmoth (while his creation Phyrexia steps into Multiuniversal), Weeping Angels when given something big enough to feed on, The Titans, the Balorean Crusade, The X Parasites, Walternate in Fringe.


 * Multidimensional Threat: Just to one up those small-timers above, these guys won't stop at a single universe; they'll cross time and space to either take control or just smash all of reality to pieces. See Multiversal Conqueror.
 * Examples: The Anti-Monitor, Ch'rell/Shredder, Galactouse, Abraxas, the Dark One, Kaiser Ephes, Dark Brain, The Edel Bernal and Gaioh, Noein, BKR, Davros and the Daleks (in the series 4 finale of the new series), in The Dark Tower,  in His Dark Materials, ~The Hitchhiker's Guide to the Galaxy~ Version 2.0 in Mostly Harmless, Unicron (somewhere between this and the above; he's a multiversal being that devours realities one universe at a time), Count Bleck  in Super Paper Mario, Brand, the Heartless, Yukari Yakumo, Professor Calamitous in the Nicktoons Unite series (not so much in his source material),  in General Protection Fault, Mary Sues, the League of Mary Sue Factories and the Enforcers of the Plot Continuum, most villains in Digimon (notably the Final Boss), Baal from Disgaea, the Mortiverse and Pun-pun from D&D 3.5, the Lone Power, The Guardian of Forever, Luther Lansfeld,  from Bayonetta, the Kromaggs, Azathoth, the Time Lords (pre-time lock),  of Doctor Who, Lord Vyce and the Entity, the Neverborn, the Nephandi as whole, especially the Aswadim, Nicol Bolas as well as Phyrexia (assuming each plane counts as a universe), the Decreator, and (it has been said but never shown on-screen as being true or false),  from Homestuck. In Fringe,  All the high ranked witches from Umineko no Naku Koro Ni, such as  . The Mad Mind of Arthur C. Clarke's The City and the Stars may not be able to do this alone, but the blowback of his clash with his benign alter-ego Vanamonde might well "ring down the curtain on Creation" when and if it happens.