It's understandable if casual fans are scratching their heads over the central conflict of "Batman V Superman: Dawn of Justice." How could Batman ever stand a chance against Superman? One is a rich guy with no super powers and the other is a virtual god. It doesn't seem like a fair fight.

However, anyone who has ever heard of Superman knows he has one main weakness: Kryptonite. Thanks to some of the trailers for "Dawn of Justice," we know the green space rock is in the movie. But since it wasn't used in 2013's "Man of Steel," Superman is not yet aware of this potentially fatal vulnerability.

"I wouldn't necessarily say it's a survivor's guilt," Henry Cavill said when discussing the "Man of Steel" aftermath. "I mean, that's a different kind of thing because he's above the threat. I think the most difficult thing for him at this stage of the story is that he has just come to terms with the fact that he is really, really quite powerful and he hasn't found any major vulnerabilities yet, and despite this, despite the enormous power that he has, he still cannot do everything, and he really struggles with that. It's not just a quick, 'Okay, I get it. I can't save everyone.' That takes a long time to work out."

If Superman isn't yet aware of his main weakness, it's fair to ask when he will discover it. Our money is on Ben Affleck's Batman harnessing it as a weapon, to Superman's great shock and discomfort. In the most recent trailer we even see Batman block a punch from Superman, which could be the first time the latter has come into contact with a substance that weakens his abilities.

Kryptonite is the great equalizer in the fight between Batman and Superman. That is how the Dark Knight stands a chance against the Man of Steel and it's also how Zack Snyder will introduce potential danger for Superman into the DC Extended Universe. We expect it to play a big role in "Dawn of Justice" - Jesse Eisenberg's Lex Luthor can be seen gazing at the green meteor in one of the trailers, after all - and beyond.

"Batman V Superman: Dawn of Justice" will finally hit theaters on March 25.