MISBELIEF. People carry beliefs about themselves, and they're not always true. The same can be said for characters. If you can define a character's misbelief about themselves, then it can drive an entire novel. For example, one of my own character's misbeliefs is that he isn't good enough. Things happened in the past to make him believe this. But through my story, he slowly comes to understand the truth about who he is.
Although Story Genius talks about using this with the protagonist, I use this with every one of the characters in my novel. It's a powerful device that moves beyond mere "want" and "desire."