Without its master's command, the restless Scourge will become an even greater threat to this world. Control must be maintained. There must always be... a Lich King!
~ King Terenas Menethil II
Dark Gaia grows over millions of years, then rises to destroy the world. And I put it all back together. We've been doing this over and over, again and again...Since the very beginning of time.
~ The balance of power between Dark Gaia and Light Gaia.
Villains who can actually serve very important purposes and need to be kept alive, imprisoned, or simply kept around. No matter how sadistic, bloodthirsty, cruel, or even how much they are hated, these villains cannot be destroyed/killed or something terrible can happen.

These characters are similar to Virtually Resourceful characters, but are obviously opposed to their alignment. These characters are usually created to keep the story relatively three-dimensional.

IMPORTANT: Pure Evils can only be Necessary Evil if they fall under the first, third, fifth, seventh, twelfth or twenty-first criteria.

Examples include:

  1. Villains who are keeping a much worse evil at bay. (Examples: Galactus keeps Abraxas, a being able to destroy universes, out of the Marvel Universe; the Lich King keeps the Scourge from becoming an even greater threat to Azeroth; The Seven Deities, while seeking a new world order, protect Gaea from the Gohma Vlitra; while the remnants of the US Armed Forces in Last of Us, despite running the quarantine zones as police states, genuinely protect the inhabitants from the Infected and attempt to help and be friendly with civilians whenever they can; Anna Morgan, whilst depicted as an abusive and mentally disturbed mother, keeps her adoptive daughter Samara Morgan from continuing her torment and killing spree).
  2. Jerk employees and employers that actually are capable of doing their jobs and it's made very clear the business cannot succeed without them. (Examples: Benson is heavily trusted with keeping the park afloat; Malcolm Tucker was very capable in doing his job as the Director of Communications)
  3. Villains preventing catastrophes, including the end of the world or universe, with their mere presence or actions. (Examples: In God of War, each time a God of Olympus dies, a different ecological disaster occurs; Kyubey prevents Armageddon with energy collected from magic girls; Kurumi Tokisaki wants to travel in the time to 30 years ago to protect the planet Earth from the First Spirit in order to prevents the death of 150 million people, Colonel McCullough has to save humanity by killing the ape species, which he fails in doing.)
  4. Some anti-heroes. (Examples: Vegeta helps Goku and the other Z-Fighters protect the universe from threats, although initially doing so out of a desire to have his own shot at killing Goku; The Punisher fights off and defeats various supervillains.)
  5. Evil vs. Evil scenarios where one of the villains is the only subject strong/powerful enough to defeat the more dangerous threat. (Examples: Lord Garmadon was the only person who could wield all four golden weapons to destroy the Great Devourer; Stewie Griffin was the only one who could stop Diane Simmons from killing Lois; Heinz Doofenshmirtz was the only one able to stop Aloyse Von Roddenstein from sending the Earth to a new Ice Age.)
  6. Business Villains that can provide a product or service that is needed or well-liked by people. (Mr. Krabs runs the Krusty Krab which produces the very well-accepted Krabby Patty; Abstergo Industries have genuinely contributed to most of society's inventions; Seto Kaiba is in charge of KaibaCorp; OmniCorp, despite violating RoboCop's human rights and removing large portions of his free will, does make the world a better place by providing automated peacekeeping machines for the American military, thus enabling them to patrol Tehran and keep it safe from people like suicide bombers without endangering actual infantry troops). This can also apply to entertainers who perform or create to please and entertain people (Pink Sheep, Misa Amane).
  7. Villains performing villainous acts that lead to beneficial results/consequences, whether the result itself was what they intended or otherwise. Some cases of this instance show where villains whom their actions was turned out only to merely trained/molded the heroes so the said heroes can became a better savior (in which they often revealed in the end). Other cases, however, show that either their actions are the key for their future downfall at hands of heroes that they antagonize or made hero realized the grave situation that everyone faced (Examples: Joe Chill murdering Martha and Thomas Wayne leads to Bruce Wayne becoming Batman; Blackfire using her sister, Starfire, as a bargaining chip for the Gordanians leads to the creation of the superhero team called the Teen Titans that ultimately fights her; Kessler antagonizes Cole MacGrath so he can be powerful against The Beast; The Ten Rings capturing and severely wounding Tony Stark allows Stark to see the harm that his company's weapons cause and leads to him becoming Iron Man; The Architect created the One prophecy for Neo and his predecessors)
  8. Rich Villains that helped the city they live in. (Examples: Lex Luthor helped build half of Metropolis; Mr. Burns is Springfield's only taxpayer)
  9. Amoral entities that must keep the balance of nature in check. (Almost every incarnation of the Grim Reaper or any Death God in mythology is this)
  10. Family Breadwinners. (Peter Griffin is often the only person in the family who actually works to put food on the table)
  11. Successful Anti-Villains. (Ozymandias united the world against Dr. Manhattan in order to prevent World War III, at least temporarily.)
  12. Villains with important information. (Hannibal Lecter had information that helped Clarice defeat Buffalo Bill.)
  13. Some heroes who turned to the dark side that had everything related to their evil actions upon their fall from grace exposed, would led to undesirable consequences. (When Harvey Dent helped locked half of Gotham's crime bosses away in The Dark Knight, he gave hope to Gotham. When he became Two-Face and killed people, Gordon and Batman knew if the truth came out, people would lose hope so Batman willingly took the blame so Dent would stay a hero after his death.)
  14. Lawful Neutral or corrupt cops who keep order, and it's obvious that situation would be worse had they not been present. (Razoul, despite being amoral and corrupt, keep peace and order in their home cities.)
  15. Hostile biological species, tribes, or civilizations that, while hostile or xenophobic, are capable of producing children and families. Killing of a naturally hostile race, civilization or tribe would still be considered an act of genocide. (Examples: The Yuuzhan Vong and The Predators)
  16. Certain Evil Teachers who keep unruly students in line.
  17. Certain Evil Alter-Egos or powerful entities within a hero, the ones that has possessed the hero, or grant them their powers, resulting in them saving his/her lives from time to time. (Examples: Zangetsu possessed Ichigo multiple times and, as a result, saved his life multiple times; Kurama sometimes possesses Naruto or gives some of his power to prevent Naruto from getting killed or to fight off a powerful foe; Yami Yugi frequently helps Yugi out)
  18. Redeemed Villains that joined, or at the very least, helped the Hero (Yasha, Trish, Bagramon when he was the Old Clock Shop Man, and many others).
  19. Villains that saved a protagonist(s), Attempt to sacrifice themselves to save a protagonist(s), or sacrificed their lives to save the protagonist(s), such as SA-X, BlueMeramon, Sybok from Star Trek V: The Final Frontier (who also qualifies for "Redeemed Villains" above); Android 16 who attempted to self-destruct to kill Cell; and questionably Nemesis from Resident Evil: Apocalypse.
  20. Double Agents that are on the side of good and pretend to be evil. These people can be either friend(s) of the hero whom assigned by heroes themselves to infiltrate an antagonistic faction/group as a means to discover their evil schemes or those whom originally at odds with heroes but ultimately chooses to switch side with the heroes and leaked the antagonists' evil scheme on them. (Severus Snape pretended to be allies with Lord Voldemort but was secretly helping Dumbledore and Harry Potter.)
  21. Dark Forms, Devils, or other personifications of evil that are literally the source of evil. If they die, the balance between good and evil would imbalance. (In The Wheel of Time, Rand discovers that if he killed The Dark One, everyone would be happy all the time, but they couldn't feel a different emotion as Evil would not exist anymore)