Gotham, a city of crime (dark), deserves a “Dark Knight” (a vigilante); but what it really needs is a “White Knight” (lawful), to inspire the people to trust the system/law again.
The Dark Knight - Batman. The White Knight - Dent.
Gordon tells the crowd at Dent’s funeral that Dent was the hero they needed, but didn’t deserve. He tells the opposite to his son referring to Batman as Batman starts running away.
Add Zimmer’s music to it, and it becomes one of the great endings in movies