Evil overlord

Implied:
* Boss battles

Usually simply eliminating this overlord will solve all the problems completely, their minions go into hiding, snap out of their mind control, return back to their home dimensions or whatever. Even if the remaining servants still cause trouble, the fact the overlord was defeated has made them mostly an annoyance rather than a real problem. Implies that the servants didn't have much heart for the conflict and causes them to buckle when the only one holding them together in the cause disappears.

The evil bit may not be necessarily true always, but the effect for the normal folk is the same as if they were.