|Katniss Everdeen is often motivated by vengeance.|
So, chances are, once your heroes have made a name for themselves, and built up a bit of a reputation, they will also have built up a pretty good supply of enemies looking for payback. These enemies might be previously vanquished foes who got away with their lives, or the friends or relatives of vanquished foes who didn’t. They could even be individuals nursing a vindictive streak born of more subtle stuff. Perhaps your heroes failed to save someone, or lost an ally under their charge only to gain great glory from their sacrifice. These things could also drive someone to seek revenge.
When working vengeance into a book or game, it is vital to raise the stakes with each attempt. A vanquished villain is not likely to execute his revenge plot unless he feels comfortable of victory, especially if it requires that he put himself in harm’s way. He's dealt with the heroes before and should be fully aware of their capabilities. A smart villain will put that knowledge to good use. He might also elect to enact a more subtle form of revenge, perhaps targeting people the protagonists care about, or attempting to sully their reputation rather than attacking by force. Some may come up with even more creative ways to enact their ultimate revenge, beyond boring old death.
Have you incorporated any particularly interesting revenge tales into your books or games?