>>79834753We already know Luthor gets his hands on some kryptonite. He also knows that Bruce Wayne is Batman. I have no doubts he supplies Batman with the stuff in order to even the odds, and that this shot only happens after Clark has been thoroughly weakened. We see Superman effortlessly knocking around Bruce in his mech-suit in another shot in the same trailer, so clearly it isn't strong enough to withstand his blows on its own. This isn't going to be a Hulk-Buster versus Hulk scenario, this is going to be Batman stalling for as much time as he can until the odds aren't stacked against him.
And then obviously something will happen that will make them realize neither of them is the bad guy here and that they need to work together to stop Luthor.
