It looks like we will finally see Jeremiah Valeska complete his transformation into the Joker in the Gotham Series Finale. I have noticed a few things about this version of the Joker. After he fell in the vat of chemicals, he supposedly became brain dead. However, ten years later, he wakes up when Bruce Wayne returns to Gotham City. We know that Jeremiah developed a twisted obsession with Bruce Wayne and only woke up when Bruce returned. It could be that the vat of chemicals were only part of the reason Jeremiah was catatonic until now. It could be he lost all sense of fun and purpose when Bruce left Gotham, but when Bruce came back he saw a golden opportunity to have another play date with his favorite victim. However, he clearly runs into someone who is far more fun than Bruce Wayne ever was: BATMAN!!! Thus the feud between superhero and supervillain begins!
This reminds of me of what happened to the Joker in The Dark Knight Returns. After Batman was forced into retirement for ten years, the Joker became catatonic and lost all sense of fun and purpose. But when Batman returned, the Joker was back to his old homicidal self. I think this is the approach the showrunners are going with Jeremiah’s character arc as the Joker. I can’t wait to find out if I am right.