The Alexandrian posted a great article a few weeks back with a great piece of GM advice: Create lots of villains – develop the ones who survive.
This ends up solving a number of common RPG problems. It’s often tempting to make the villain invincible until the final battle in order to keep the story going, or to play up the evilness of a villain to a party that just doesn’t care much about him.
However, if you add a host of villains and let the heroes dispatch them where ever they can, you won’t get attached to them. You’ll keep player agency intact. Most importantly, as certain villains continue to survive, grow stronger, and really meddle with the player’s goals, their hatred of him will be natural and all the more satisfying.
There’s a connection here to Dungeon World concept of Fronts, but that’s another post.