I thought the devlopment of Two-Face in this movie is very, very well done. If anything that's a "dislike" about TDK on two fronts. On the first front there's no "development" of The Joker's evil. He just is,
See, to me, that's something I like about it. I don't think we should
see the Joker's development into the monster he is; he's not supposed to be a psychologically realistic character the way Harvey Dent is. He's an archetype, an elemental. He's Coyote and Loki and Mars and the Grim Reaper wrapped in one, smiling package.