pawsplay
Hero
And Batman does regularly defeat superhumans, such as Killer Croc, who has superhuman levels of strength.
And because he has Kryptonite, he can beat Superman. But that's the only way he'll beat Superman. He can slow him down but other than that there's just no way for him to beat Superman. Even with enough prep time.
Actually, that's not true. Batman hs beaten Superman without Kryptonite before. In one case, knowing Superman's scruples, he rigged himself with a detonator and used a hostage (Superman did not understand Batman's psychology well enough to realize that the "innocent person" Batman specified as the victim was Batman himself).
Further, Superman (in most versions) is not completely invulnerable. While his battlesuit in the Dark Knight series isn't quite up to snuff, that was really just a ploy to get Superman into position, relying on Superman's tendency to resolve all tactical conflicts with his fists. In a proper ambush situation, Batman's mastery of technology is sufficient to take Superman out.