Phantom Limb: "We're not so different, you and I."
Brock Samson: "Yeah, I don't need another 'We're not so different' speech. I get those a lot."
Phantom Limb: "Yes, I'm sure you do."
There's a strange intimacy that exists between antagonists and protagonists. The dynamic interplay of their differences creates both attraction and friction in a dance of interconnectedness. Despite their enmity, they are drawn into each other's orbits, each one's movements influencing the other. One is driven to create Chaos while the other's passion is to preserve Order. One is driven to commit the crimes that the other is dedicated to stop.
They are Lex Luthor and Superman, one striving to freely exploit as much of the world as he can while the other champions life and freedom for all.
They are Moriarty and Holmes, linked by the crafting of criminal intrigues versus the drive to unravel challenging puzzles.
They are any politician's image and the image of the politician's opposition, each contesting to propagate the best lie.
In characters, the simplest form of the dynamic may exist between one character seeking a goal and the other blocking the attainment of that goal. Very often, at least one of the two will hate the other. In the more complex dynamics, the two may have begun as friends and, though their choices have put them at odds, there could still exist a measure of respect between them--if not mutual, at least one for the other.
Their backgrounds often serve to highlight the friction between them, whether they perceive themselves as having come from a loving family environment or one fraught with tension. Do they consider their formative years to have been easy or difficult? A protagonist will usually see their life experiences as the foundation for positive growth. Some of the most bitter antagonists can go through the same experiences as the protagonist they oppose yet find excuses not to grow at all. The most complex antagonists will find justification to respond to their struggles in such an extreme fashion that while the hero might consider their paths to differ greatly, the hero can still understand the choice of his opponent. Perhaps more importantly, readers can accept it as a viable choice that they themselves might have made.
Professor Xavier and Magneto are prime examples of opponents locked in a dynamic where two friends came to be at odds by choosing differing paths to achieve similar goals. Both characters want to see the world grow into an environment where mutants can live safely. Xavier believes this can be achieved through peaceful coexistence between mutant and non-mutantkind. Magneto believes this is only possible if mutants rule over society. He respects Xavier's efforts, even supports them, but his own suffering at the hands of Nazis has soured his faith in the potential of humanity's goodness and a special intolerance for racism.
In a relationship of such complexity, hero and villain might ultimately come to a point where, even though they continue at cross purposes, they recognize a validity in each other's mission. By that, meaning that while they don't kiss and make up, they don't go out of their way to oppose each other directly either.
Is there a hero-villain pairing that resonates with you as being particularly profound?