Back in 2002 or so, a Batman Vs. Superman movie almost made its way on to the big screen.
It went so far as having Andrew Kevin Walker (Se7en, Sleepy Hallow, 8MM) write the script with a revision from Akiva Goldsman (I Am Legend, Batman and Robin, Batman Forever).
Well the Andrew Kevin Walker script has made its way back online and can be read here.
Here are a few details which includes the revised script (via MysteryManOnFilm):
Starts off with a terrorist attack where Superman catches the perpetrator. The people want to kill the terrorist with Superman not letting that happen, lecturing the people. As Superman flies away with the terrorist, the terrorist blows Kryponite dust into Superman's face and escapes leaving behind a strange mask.
Bruce Wayne gets married where it's revealed he has retired from being Batman. Clark is there where it's also revealed he is getting divorced from Lois.
Bruce's wife is murdered with her face being transformed into a Joker-face.
Bruce heads to the Batcave seeking revenge where Clark confronts him, and they have a conversation about killing etc. Bruce is enraged, throws something at Clark telling him to get out.
The Toyman is featured as Batman investigates the dart that killed his wife. He asks the Toyman who is impersonating the Joker, with Toyman stating The Joker is alive etc. (as it's set in the same continuity as the previous Batman and Superman movies).
This all leads to a confrontation between Batman and Superman, where Batman wants to kill the Joker while Superman won't let that happen.
The big Batman Vs. Superman battle culminates with Batman having a kryptonite-laced suit and an arrow. Superman gets shot in the shoulder with the arrow; Batman breaks off the arrow leaving the kryptonite tip - as he has to do what he has to do.
Batman confronts Joker where it's stated that Bruce's wife was never his in the first place - the Joker created her!
Long story short, Batman and Superman begin to battle against The Joker and his goons. It comes down to Batman killing Joker with Superman stating if he does it, to take off the mask. Batman doesn't do it - then Lex Luthor shows! Luthor is wearing his battle armor where there is an all-out battle between Superman, Batman and Luthor.