Why is Batman willing to fight Superman rather than give up control

Superman and Batman go back many years. During that time, Superman has come under the influence of the President of the United States and acts as a tool. Clark claims it is a promise that was made to keep them in line, but he truly seems to be the president's puppy dog. While Batman appears to be the stronger one of the two ideologically, Superman seems to have caved to outside influence. When the president calls on him to put Batman back in line and make sure he behaves, Clark is all too eager to oblige. Even though Clark is aware of Bruce's true mission, he seems to disapprove of the actions.

On more than one occasion, Clark meets with Bruce to tell him what is going on and to see if he will stop his latest quest and bury Batman once and for all. Bruce does not agree and Clark goes so far as to tell him that this latest directive comes from the president. Still, Bruce does not care; he is on a collision course with destiny. Superman, however, still answers his own call to help humans. This is especially evident when he comes to the rescue and makes the Soviet planes crash into each other, and then again when the nuclear bomb is threatening to explode into the earth. His path is different from Bruce's in this way. Bruce is out to save a corrupt city, while Clark is out to save a corrupt planet. Clark's methods, however, do not appear to put anyone else's life at risk except for his own.

Superman meets Batman's challenge head on. Although he is still recuperating from the nuclear blast that has sapped most of his energy, he is determined to defeat Batman. He mistakenly believes that he kills him during their altercation. It is only as people are leaving the cemetery that Clark hears Bruce's heartbeat and knows that he is actually alive. He winks at Carrie to indicate that he knows, but he also knows that Bruce in his own way has won. Bruce will continue on his mission.