10 Comic Book Betrayals We All Should Have Seen Coming
7. Batman's Secret Files On His Teammates - JLA #43-46 (2000)
During the Tower of Babel storyline, Ra's Al Ghul took down the entire Justice League by exploiting their weaknesses. After he froze Plastic Man, crippled Superman with Red Kryptonite, and made Green Lantern go blind, the remaining Leaguers couldn't understand how Ra's was able to defeat them so easily.
Eventually, the JLA learned the deranged alchemist had accessed Batman's dossier and used his data to figure out the simplest way to take down each superhero. The League were horrified, realising that Batman had analysed and compiled each member's strengths and weaknesses without their consent. Although Batman stated his data was crucial in case any of the superheroes turned evil, the Justice League felt like the Dark Knight betrayed their trust and so, encouraged him to leave the team.
However, Batman's actions aren't that surprising since... he's Batman. Despite having no superpowers, the Caped Crusader usually comes out on top because he has a plan for every contingency. Because the League have been brainwashed on multiple occasions, having a system to immobilise them sounds logical. Considering Superman was mind-controlled shortly after and nearly killed innocent people, it would be unreasonable for Batman NOT to learn how to incapacitate his teammates.