While there are some awesome Batman villains, I agree.
None of them have the dynamic the Joker does. The Joker is like the complete opposite of Batman. Chaotic, maniac, big smile, kills without a second thought.
All the Joker tries to prove is that anyone, no matter how just they think they are, no matter how steadfast they believe themselves to be, are only a single bad day away from turning into a monster like him.
He wants to push Batman over the edge, because Batman is the biggest challenge in that regard. If he can bend Batman, he can bend anyone. So if he can get Batman to kill him, his point is proven.
The rest of the rogue’s gallery does in fact have better dynamics with Batman than Joker does.
Joker’s some lame ass loser who views supervillainy as a career while literally everyone else in the rogue’s gallery has better, more interesting reasons to do what they do. Joker’s doing evil for the lulz schtick is boring as fuck. He’s nothing but a boring-ass two dimensional Gary Stu and I am tired of being quiet about it.
The only interesting Joker we’ve had in the past twenty years is the Joaquin Phoenix one.
