Extremists

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. Some are also heroes that believe that crossing the line is needed when enforcing the law. However, Extremists have not (at least publicly) crossed the legal line into outright terrorism.

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 work for political purposes while an anti-villain's goals are more general.

Religious extremism, racist organizations that do not become outlawed (in their native country), and individuals/groups who hold extremely controversial, often hateful views, yet are not officially considered terrorists can be added here.

For more information, read up on Hate Groups. Those listed as "Non-Outlawed" would be acceptable here, as would some extreme "fringe" groups, non-outlawed cults and so forth. Do NOT use this as an excuse to create propaganda designed to demonize a certain group or people; they must have established facts showing they are what most would consider a destructive cult or similar.

There are heroic counterparts to these villains.

These villains aren't Pure Evil, since extremists are mostly anti-villains with noble goals that go too far with it being more than mere delusions, even if they have crossed the moral event horizon and have committed horrific acts.