The Joker does not want to rob banks. He wants to prove that Batman's discipline will break, that the line he holds will eventually give way under enough pressure. Magneto knows exactly where Professor X's idealism can be turned against him. The nemesis in great stories is rarely just an obstacle. It is a mirror, showing the hero what they most fear about themselves.
Scripture calls our adversary by name. He is not a metaphor. He is described as a roaring lion, as the accuser, as a deceiver who masquerades as an angel of light. He knows your specific vulnerabilities because he has been studying them. And he is not the only nemesis, but his work often employs the flesh, the patterns of our old self, and our shame, all of these function as forces that oppose your heroic development.
In his book The Screwtape Letters, C. S. Lewis cleverly revealed many of the ways Satan works on each of us to undermine us. The book is a series of letters from a mentoring demon, Screwtape, to a more junior temptor, Wormwood. In the humorous communications, Lewis helps us see both the techniques and the motivations of why Satan’s demons would want to hinder us from being our best selves, thus hindering our usefulness for God’s kingdom.
Our nemesis weakens as we understand how he works on us and why.