1. The Anti- Monitor
A character who was the villain of the mini-series Crisis on Infinite Earths in 1985. The ruler of the universe of anti-matter, he began destroying other parallel universes to cause his to expand and increase his own power. As part of the fight against him, several different worlds were merged into a single one. This was all intended to simplify DC Comics continuity, but eventually things were judged to have got confusing again. There would be two more reboots, Zero Hour and most recently Flashpoint. The advantage of using the Anti-Monitor is that the heroes could be in their own worlds at the start of the film, and then meet each other for the first time, to deal with the threat to all existence. This explanation also gets round the question of why none of them have meet up before. At the end, the worlds fuse together and all the heroes are in the same universe. So the film ends with a new range of possibilities for franchise launching. So, anyone you'd like to see in the Justice League Movie? Do let us know...