You’re referring to the Joker? I watch The Dark Knight because of the Joker and Two-face (both Heath Ledger and Aaron Eckhart are why the movie’s great, yet Christian Bale is bland in it).
I disagree (although understand your opinion). The meaning of The Dark Knight is subversion (like all great art); the Joker was never the main antagonist, but to setup the idea Harvey Dent had to spend most of the movie as just Harvey Dent. However he did spend about 30 to 40 minutes as Two-face (maybe not literal screen time, but the length of the movie which he was the change).
Two-Face is the true villain of The Dark Knight, but to make the idea cool meant the compromise of giving the Joker much more screen time (and I honestly think Aaron Eckhart is the primary reason the movie’s great, as good as Heath Ledger is in the film).
Since when are you the critic?
The ending of Dark Knight was rushed, and no matter how you try to spin it with your meaning making apologism, Two Face dying at the end was a total letdown.