3. Disagreements
The balance scale that Lady Justice holds in her hand weighs truth and fairness: Batman's scales are used to weigh pain and fear. Usually, the scales will weigh in favor of fear and bad guys will repent and avoid the Bat at all costs. Well, the smart ones will, at least, but most of the villains will go back to their ways and this is why Batman's always off trying to foil their plans, making sure they end up back at Arkham. It'd be easier if Batman could kill, way easier; Gotham would be a virtual utopia if Batman killed everyone in Arkham, but he doesn't. Other superheroes have actually killed and the deaths were either justified or a result of some bad brainwashing, so it was understandable. Hal Jordan killed a lot of Lanterns, but give him a break, his entire hometown was wiped out and he had a slight mental breakdown. Wonder Woman had to lay the law down when Max Lord was mind-controlling Superman, but I don't think Batman would approve of Wonder Woman's actions. No doubt he would beat the crap out of Max Lord and even paralyze him from the neck down, but he wouldn't kill him. This is where the Justice League would have the bulk of their problems. If there's anything we know about Batman, it's that he's particular (and that's putting it lightly). It's not necessarily a bad thing - we like that he's particular and has his own way of doing things - because in the end, it all works out. But you can't tell me that's going to fly (no pun intended) with the rest of the JL; there are leaders and followers on teams and Batman is neither. He doesn't follow the pack and doesn't expect anyone else to follow him, so good luck getting him to go to the mandatory team meetings every other Wednesday.