I would like to take a moment to note that I’m going to discuss the Killing Joke. The book, not the upcoming movie.
Specifically, I’d like to discuss its end. If you haven’t read it yet, I’m going to spoil the fuck out of it for you. So you might want to read it first and then come back.
However, before you go, I’d just like to tell you that that Trinity, Dumbledore, and Jesus all die at the end.
John, however, does not. (I know, right?)
There, that should’ve been enough text that there are no spoilers in the blub-box if someone posts this to Facebook.
So, TLDR: the Batman kills the Joker.
The very first panel of the book, that takes up the entire first page, opens with the same dark-water-with-rain-drops that finishes the book. The next panels, with no written dialogue/exposition/thought bubbles, show Batman going to speak with the Joker in Arkham. The first words of the book are the first words of the Killing Joke, followed by Batman’s final thoughts before the Killing Joke. In the conversation with the Joker-imposter, Batman, very explicitly, talks about what will happen at “the end” and says “[w]e’re going to kill each other, aren’t we?”. He goes on to clarify that “[p]erhaps you’ll kill me. Perhaps I’ll kill you. Perhaps sooner. Perhaps later”. To emphasize the point, Batman says he was making an attempt to talk things over and avoid someone’s inevitable death, “just this once”. And Joker never even heard the final offer, because he’d already escaped.
The final scene in the book’s last two pages before the fade-to-black-water-in-the-rain, is the Joker’s last joke and its effect. That joke is, literally, the killing joke. It’s the joke that gets Batman to finally end their game, truly finish it. The joke itself centers around a pair of lunatics, escaping together from the constraints of sanity. .But the joke never really makes clear – which of the two of them is the inmate with the flashlight.
On the fourth panel of the final page before the fade to black, Batman and the Joker are alone, laughing together in the rain. They hear a police car approaching.
The fifth panel shows Batman having lunged forward, almost certainly prompted by the approaching police car. Police, who would simply arrest Joker and send him to Arkham again, before he escaped, again. We can be certain that the panel shows Batman lunging for the Joker, because the Joker’s torso is forward the moment before, and then is bent backwards in the sixth panel. Notice the angle of his legs; his feet are planted but he’s off balance and would be falling if it wasn’t for Batman’s hands grabbing him. Batman’s hands are clearly grabbing Joker, but his hands aren’t near Joker’s throat. As such, it’s a poor assumption that he strangled Joker or broke his neck.
The sixth panel only shows us Batman’s cape, Joker’s outstretched hand held open with the palm up, Joker’s laughter, and the squealing of the police siren.
The seventh panel shows Batman’s foot, and both of Joker’s shoes: his left shoe has a very clear red spot on the toe that’s not caused by any light around it, as it’s the only red patch, and is illuminated by the police car’s headlights. Joker and Batman are standing in a puddle that’s bisected by a bright line/beam that’s perpendicular to their shoulders. There are two patches in the puddles, the lower of which appears to be a patch of ground that’s at higher elevations than the surrounding turf, and has been stained red. The upper patch of color, however, is clearly a red liquid, because we see a ripple in it from a rain drop. Around those two patches of color, the water on the ground is glassy black since the circus lights are behind Batman’s back. Therefore, they are not casting any light in the puddle. The light we do see is coming from the side, from the police car’s headlights. It’s a beam of yellow light, and does not contain any red
With the red blobs’ appearance, Joker’s laughing has stopped abruptly and entirely. The police siren is still squealing.
The eight panel has only the puddle, and a single red shape, apparently the lower of the two shapes from panel seven. The shape is biscected by the same beam/ray of light. The red shape is only being illuminated by the yellow/white of the police car’s headlights, confirming that the dirt’s been stained red with something. The siren has stopped as well.
The ninth and final panel has only the puddle, no light, no color, no sound.
The beam of light has gone out.
Batman didn’t strangle him, or break his neck. His hands weren’t on Joker’s neck. But they were, however, in the proper place to tear Joker’s throat out right where the clavicle meets the neck.
The Joker abruptly stopped laughing, because he’d just had his throat torn out.