There is a bit of wondering going on about the role Kryptonite (the fictional substance that is Superman's weakness) will play in the Man of Steel sequel, tentatively titled Superman v. Batman. The thinking seems to be that the two characters will eventually duke it out, with Batman employing the special K as an equalizer in face of Superman's obvious physical advantage. I'd prefer it if the filmmakers found another angle to bring these two men together. I share the opinion that Superman defeats Batman, period, no explanations, no conditions, no excuses.
The "Batman v Superman" name is a working title only, and there isNO NEED to have these two characters fight. We can leave the Frank Miller tale where it belongs, in DC's "Elseworlds" sagas and let these two men meet under more realistic circumstances. In any event, even with kryptonite, Superman would likely win in a heartbeat. His skill set, ie, powers, are too many and overwhelmingly superior to Batman's skills and expertise. It would just strain credulity and lessen the reinvigorated Superman brand. More interesting, intriguing and with greater plot potential and character development would be to have the two heroes circle each other with suspicion, each considering the other as an abomination and contrary to everything each of them stands for. And, as the plot's crisis mount, the two find themselves in common cause and discovers that each has abilities and skills that come in handy in the fight against evil. This way we can have Batman's using his skills in detection and strategy with more purpose, and we get to see Superman be super against a foe, we assume, who can give him a fight worthy of his strength.
On the matter of Kryptonite, let me add that that the filmmakers would be wise to just get rid of. I always resented the fact that the most powerful being in the universe could be rendered weak and eventually killed with a mere radioactive rock. It doesn't do any good to hypothesize alternative theories around this; Superman is a character who is able to withstand immeasurably destructive cosmic forces and it is irrational for a hero of such heroic resilience to quite suddenly lose his strength and commence to perish because of a rock emitting a particular kind of radiation. It has never, never been plausible, even considering how insanely implausible (albeit entertaining) his comic book world is.
Kryptonite is, and always has been, a fast exit for writers who hadn't the imagination to create better, more demanding perils for Superman to face. It had gotten to the point that seemingly every two-bit punk and shoplifter had a chunk of the green stuff in reserve in case Super tried to interfere with their acquisition of ill-gotten goodies. We have to consider as well two other inconsistencies with the fictional rock; (1). If a rock emits radiation powerful enough to weaken and eventually kill the otherwise invulnerable Man of Steel, why have humans, in most of Superman's 75 years, been able to handle the substance without harm. This was a glaring inconsistency, an issue unresolved because the writers wanted human villains, be they punks, technologized billionaires, or mega-powered bad guy, to be able to handle the material to foil Superman and then move on with their agenda. It's a cheat in the narrative art.
By rights, humans should burst into flames and scream something horrible before there is nothing but a black scorch mark on the ground where they once stood. Kryptonite should have been killing humans all along.
(2). Why has it seemed that every single chunk of Kryptonite landed on Earth? Over the many decades that I've read Superman, it has always seemed that the kryptonite was much, much too plentiful. Even in the comics, the universe is a very big place and it would seem only the smallest, nearly unmeasurable amount of K would crash to earth. What I am basically arguing is that Superman's only weakness should be someone with superior strength, skills, intelligence. The Kryptonite trump card has got to end. And DC should run another Dark Knight novel with an alternative ending--Batman picks a fight with Superman and Big Blue, annoyed, goes Full Zod on him. If you want some of Superman, you're gonna get some of Superman. As they say, you mess with the bull, you get the horn.