10. Joker's Endgame - Batman: Endgame
It is well known that Joker does not have any superpowers and is almost always portrayed as a normal man, with insanity being his only defining feature. However, in his Endgame plan, he was able to convince the Dark Knight that he was actually a metahuman that has been a part of Gotham for centuries.
Starting with an attack on the Justice League, the Joker was actually able to turn the entire league against Batman using special laughing gas created for each league member, even Superman.
Then it is revealed that one of Batman's allies inside Arkham Asylum was actually the Joker wearing a new face after he had cut off his old one in prison. In fact, the Joker had found a specialised pool of healing liquid similar to a Lazarus pit that gave the Joker near immortality.
One after another, the pieces of Joker's final gamble to defeat the Caped Crusader fell into place. His allies were attacked in horrific ways, and a new Joker gas formula similar to the one used on the Justice League. This gas was spread across all of Gotham turning thousands of innocent people into insane monsters focused on killing everyone they saw.
In the end, the Joker may have lost his final gamble, but he also dealt a massive blow not only to Gotham but to the Dark Knight as well. For a time, it seemed that the Joker had finally finished their rivalry for good.