10 Villains Who Outsmarted Batman
8. Lex Luthor Joins The Justice League - Justice League (Vol. 2) #30
There is literally no character in the world who can match how smug Lex Luthor is when he manages to join the Justice League.
While this initially appears to be because he legitimately wants to do good, it later becomes clear that Luthor had pulled the wool over the Justice League's eyes, and is still pretty damn evil. This is especially embarrassing for the Dark Knight, because he was the one to convince his fellow members that it was worth having the questionable baldy in their team.
As such, the egg is well and truly on Batman's furious face when Lex defects, as he does so with a considerable amount of League secrets. Maybe Batman's trust issues are for the best, when things like this appear to happen so commonly.