Source: oyester.com

8. He Doesn’t (And Shouldn’t) Have a Definitive Origin

Yeah, this is another thing most protagonists need: a backstory.

Some context to a character to understand where they're coming from. But The Joker only exists as a fully formed villain character with a mysterious history. He doesn't have a provable origin which is what makes him so scary.

And I'm sure some of you are saying "but isn't the new movie an origin story that will show how he became the Joker?" and the answer is "yes, but that's why it’s a dumb idea."

No origin story you can give the Joker is going to match up to the ones we've all created in our heads. No matter what it will be underwhelming.

And again, you might be wondering "well, do you also think that Three Jokers comic that's coming out is dumb and a bad idea?" and to that, I have to say "also yes. Duh."