Extremists are villains who have well-intentioned goals for the greater good, but whose methods and ultimate ends are very extreme, to the point that the heroes have no choice but to stop them. Sometimes, extremists can go too far with their actions, to the point where they cross the Moral Event Horizon and become straight-up delusional villains who think that they are saving the world by removing free will, for example. Some are also heroes that believe that crossing the line is needed when enforcing the law. They do not often cross the same lines as a terrorist, but it is possible for a villain to fit both categories if the extent of their crimes is ultimately for a noble cause.

Although monitored heavily by authorities and often despised by the public, these Extremists are dangerous and unsettling in the fact they are working within the law (albeit the very fringes of it) and may have many supporters for their cause, although they sometimes work for themselves and do not work directly under the government. Furthermore, some can win the approval of the public as long as they don't go too far.

Extremists are similar to anti-villains, because they have noble goals. The main difference is that extremists commit utterly heinous acts for a cause they genuinely believe to be a just cause, while an anti-villain's goals are more understandable and sympathetic. Extremists can live their whole lives believing it's okay to do evil things for a greater good, even if they are Affably Evil or care about many people, which can possibly be a big problem in their professional, social, familial, and romantic relationships. Some of them are Tragic or even Fallen Heroes who "learned" through their experiences that "extremism is the way to go."

Note: These villains are NOT Pure Evil, since extremists are mostly anti-villains with noble goals that go too far with it being more than mere delusions, even if their actions are not approved of. Pure Evil villains that commit horrific acts out of their own twisted or hypocritical causes should go under Terrorists‏‎, Vengeful‏‎, Jingoists, Fanatics, Delusional‏‎ and/or Xenophobes instead of this category (e.g. Unalaq, Light Yagami, Albert Wesker, Zamasu/Goku Black, Sentinel Prime, Judge Claude Frollo, Ultron, Lord Cutler Beckett, Colonel William Stuart, General Mandible, Emperor Belos, High Evolutionary, John Ratcliffe, Funny Valentine, Masayoshi Shido, and King Runeard).

Also, DO NOT add characters like these even if they are not Pure Evil:

• Villains who knowingly lie about having good intentions as a cover for their evil actions (e.g. Dawn Bellwether, Kenny Brian Meaner, Erik Killmonger, Adam (Hazbin Hotel), Odin and Tigerstar).
• Villains who sincerely believe their actions are just but it's only due to their warped/self-serving standards (e.g. Screenslaver, Wilson Arch, Doma, Bane (Nolanverse), Ultron (MCU), Kent Mansley, Riddler (Reevesverse), Lute, Kai Chisaki, Antón Castillo, Fred Waterford, Karl Heisenberg and many versions of Lex Luthor).
• Villains who genuinely started out with good intentions but lost them over time (e.g. Darth Vader, Koba, Walter White, President Alma Coin, Malcolm Merlyn, Clifford DeVoe, Kingpin (MCU), Superman (Injustice), Gangrel and Bradford Buzzard).

This is only for villains who have genuinely noble intentions/goals but use extreme and questionable methods in order to achieve them.