5. The Murder Of Sarah Essen
The epic storyline 'No Man's Land' saw Gotham City transformed into a post-apocalyptic wasteland in the aftermath of an enormous earthquake which shook the city to its very foundations. The Joker sat it out quietly, at first, waiting as the likes of The Penguin and Two-Face fought it out among themselves for land and general supervillain supremacy. It couldn't last forever though. And, as Batman returned to Gotham (following an uncharacteristic crisis of faith) so too did the Joker's more vindictive streak.
Just as things were beginning to look up for the denizens of Gotham, The Joker struck. After fooling about with Huntress and power-mad cop William Petit (kidnapping the latter's men, dressing them up as Jokers and tricking him into shooting the lot of them), Mr. J marked the impending close of No Man's Land with a threat: to kill every child born during the crisis. Detective Sarah Essen - wife of Jim Gordon - confronted the clown, alone, at police headquarters.
While Sarah managed to save the children from the Joker's wrath, she bore the brunt of his cruelty, taking a bullet to the head for her trouble. Even Gordon's fury didn't faze the Joker; despite the cop shooting him in the kneecap, he saw the funny side.