Actually, kryptonite isn't Superman's only weakness.
His uncompromisingly upright morality often constitutes a tragic flaw which comes back to haunt him when he's faced with a foe too powerful for him to imprison. He's forced to either let the enemy go, knowing that the villain will kill again and Superman will bear some culpability, or kill the foe, suffering crippling remorse which inevitably impairs his super duties.
In comparison, Batman is gifted with a ruthlessness and moral flexibility which allows him to make the hard decision and sacrifice his own morality for the greater good. Which is why Batman has a plan to kill Superman if he should ever have to, while Superman would find the very idea of a plan to deal with rogue superheroes abhorrent.
"The worst part about these reviews is they are [subjective]--and their scores often depend on how drunk you got the media at a Street Fighter event." — Mona Hamilton, Capcom Senior VP of Marketing
*Image indefinitely borrowed from BrainBoxLtd without his consent.
