Joker (Earth-99)

"What are those? Mementos from Batman's greatest victories. You mean trophies. Um, yeah."

- Kara Danvers and Luke Fox

The Joker was an enemy of Batman.

Enemy of Batman
At some point, the Joker became an enemy of Batman. He was eventually murdered by the vigilante, and one of his playing cards was kept as a trophy at Wayne Manor.

Former Equipment

 * Joker Card: Prior to being murdered, the Joker owned a playing card. It was taken by Batman and kept as a trophy.