IIRC, Scarecrow, got a dose of his own medicine at the end of the first movie, & messed him up a bit, making him "think" he was a hero.
As for the movie, I thought it was mostly crap. For one thing, I'm not a Frank Miller fan(not that I've seen everything he's done, but, I don't care for Punisher, or his rendition of Joker). It's too dark for my liking, so much so, that most of the movie was boring. I just didn't have a good time, & the movie seemed like it should've ended after about an hour & a half, as it was way too long, that just made the movie even more boring. Joker sucked, plain & simple. Don't get me wrong, Heath did at playing the role of some random psycho who likes to wear make up, but, as a Joker in general, sucked. May not be his fault, since I'm sure they gave him the basic role in that direction. He was plain boring, just went around killing people.....yippeeeeeee. That's the story of Dark Knight, a guy calling himself the Joker, goes around killing people, oh, & Harvey Dent is trying to clean up the city, & becomes 2face in the process. Wow, what a story.
If anything, I was thinking, that it seems like Heath was playing a villian Mr. Zsasz pretending to be the Joker. Hell, the Joker is supposed to be the polar opposite of Batman, & I just didn't get that vibe from this film. Mark Hamill is the best joker to date, though, I don't know that he would be able to portray him in a live action film.
Christian Bale, just as he was with the last movie, is a boring Batman & Bruce Wayne, he's lacking something, & I'm not totally sure what it is. Generally speaking, I'd say Michael Keaton was the best live action Batman, however, I don't like the fact, that his Batman, would kill AND use guns, which are 2 things, that Batman wouldn't do(though, he used too back in the 40's, they changed that). Kevin Conroy is by far, for me, the best Batman ever! He just plain rocks, he's got both roles down perfect, & without sounding like he has 40 grit sandpaper in his throat! See here
I think I like Harvey/2Face, but, as time goes by since I saw the movie, I'm starting to find him forgettable. There were some scenes in the film that were amusing, like when Joker was in that nurses outfit, & coudln't get all the bombs to explode. But, man, it was boring, an example, the scene where they are driving thru some tunnel, & the Joker is trying to kill Harvey, I don't recall any music or anything, but, it seemed like there should've been. It was just long shots of vehicles driving, & some guns firing, blah, blah, blah.
I will say, that I was never impressed with the original movie, but, I kind of like it now. The main thing I like though, is the other characters, mainly James Gordon(he did great in both movies), & Lucious Fox, & Alfred Pennyworth. They were cool. Oh, I like the Scarecrow, & Liam Neeson as Ra's al Ghul was great! That's about all I can think of at the moment. While the movie wasn't the worst thing I'd ever thing, it just was boring, & some of the main character's stank at playing their respective roles.