If you are completely and utterly confused by this, I have another story up called "Battle of the Fans." In that story, I post the character meetings and the endings that most people have voted for. If you don't mind missing the meetings, then continue on reading.
WARNING: If you do not read the other story, starting on Chapter 3, I will just post the endings. You will be completely confused by that point.
Batman threw the batarang at his own feet. It exploded into a puff of smoke, allowing Batman to be hidden from sight. He launched two more batarangs, this time at Magneto, whipped another one out, and threw that one too. The smoke was going to clear soon so he pulled out his grapple gun planning to get to a taller building, hopefully one hidden in shadows. When he looked back in the direction of his enemy, the third batarang was hurtling towards the Dark Knight himself. It stuck itself in his arm.
He pulled it out and let it hit the floor. The smoke was now clear and Magneto was now hurling himself at Batman, tackling him. As they fell, Batman jerked his elbow upward, hitting Magneto in the nose. He jerked back, long enough for Batman to roll himself on top of him as soon as they hit the top of the building. He backflipped off and again pulled out his grapple, this time shooting it at Magneto, who deflected it with his mind, sending it whizzing back at Batman.
It hit him in the gut, pushing him back down. As he fell, Magneto yanked an explosive batarang out of Batman's Utility Belt, plunging it into the Dark Knight's back. The roof underneath the Bat collapsed, creating an awkward circle. Batman clung to the roof, somersaulted back up and dropkicked Magneto, who was sent toppling off the edge of the building. Batman dove off after him, rolling when he hit the floor, and looked around, gathering his bearings. There was no one in sight.
Above him, Magneto was floating. He had known Batman wouldn't think him dead and would follow him down, so he had decided to go where the Dark Knight wouldn't look right away. However, he would be found soon, so he had to attack quickly, before that happened. He quietly detached a pipe from above, using his mind and pure strength. When it was free, he threw it at Batman, who turned at the sound of it flying through the air. He ducked at the last second, and it still managed to nick him. Blood slowly gathered up and slid down his head.
Standing up, he quickly jumped backwards, finding handholds and footholds almost immediately, and began to climb the building as fast as possible, trying to get up before Magneto could fly away. The villain laughed and simply rose higher. The next handhold he grabbed crumbled at the touch and he fell back down. Magneto knew he had won and turned away, no longer bothering with the man.
He felt something wrap around his foot, and he looked down. He saw the glint of metal and pushed it away with his mind. It bounced in the air, but stayed where it was. He frowned. Then he saw the rope that it was attached to, which was near invisible. It was wrapped around his foot, not the metal. Grapple, he thought, and as soon as he thought it, he was yanked down, his head hitting the cold gravel.
He pushed himself up, furious, and looked around for his opponent. It took him a moment to realize Batman had run away, the coward. Suddenly, he saw a dark shadow, growing bigger and bigger. Whatever was producing it was falling and it was the shape of a man. When it's descent was slowed, Magneto knew exactly what it was. Or rather, who. His suspicions were confirmed as a boot connected with his face. He shook away the pain, managing to keep himself upright at the same time, and grabbed the boot, pulling it down to the ground instead. The Dark Knight slammed into the pavement with a grunt of pain.
Magneto grabbed another pipe from above him and slammed it against Batman's head. Batman had trouble keeping down a scream. He felt himself being lifted into the air and looked down at Magneto. He barely caught a glimpse of the man before he was slammed against a metal wall. He thought it was a sheet of steel, but didn't know for sure.
He tried to move, but Magneto was holding him tightly in place. The mutant laughed as the metal sheet folded down around the Dark Knight. He fell down to the ground. He was almost crushed in his metal casing but survived. The metal suddenly unwrapped itself and a pile of bricks that had been above the steel sheet on the building it had been on fell onto Gotham's best detective.
Magneto smiled at the sight. What many had called their greatest challenge, he had beat in less than twenty minutes. What more proof did he need to know that he was the world's greatest, strongest, and most powerful being ever?