9. The Torture Of James Gordon
There are iconic stories throughout the history of the comic book industry that have become nothing short of infamous since their initial release. Without question, The Killing Joke will remain one of the most famous Batman stories ever, and not just because of THAT ending.
With the Joker being the main villain, there were always going to be crimes and actions to the point that no other villain could have believably committed them. There was physical and mental torture, the grim assault on Barbara Gordon, and even though Oracle was put in a wheelchair, her father was forced through a disturbing trauma at the same time.
To reiterate, with the Joker involved there is always the risk of crossing a line, but this was just too dark for anyone to enjoy. After paralysing Barbara with a shot to the spine, Joker stripped her naked, took a handful of incredibly distasteful pictures while she was bleeding out, and forced her father to look at them while he was chained up in an abandoned amusement park.
There is creepy, and then there is this. The disgusting and unnecessarily sexually-driven torture of both Barbara and her father, all as part of Joker's bigger game with Batman.