Harvey Dent's Transformation into Two-Face

Harvey Dent in The Dark Knight adopts a worldview of chaos and randomness after losing his loved ones and being disfigured, believing that the world is intrinsically unpredictable and that every conclusion is equally valid. As Two-Face, Dent becomes violent and causes distraction, frequently targeting criminals or people who have offended him.

How does Dent's story parallel the rise and fall of an underdog figure?