A typical tragic hero is first and foremost, born of noble stature. This gives the hero something to fall from, so they can "fall from grace" (Avril Lavigne, Nobody's Home). Blanche Dubois born in Laurel, Mississippi, to a wealthy family. She is a former schoolteacher who had been evicted from Belle Reve (a family home) after being declared a woman of loose morals. This was because years earlier, Blanche's husband committed suicide after she expressed her distaste on his sexuality. She later had many affairs trying to numb her grief on the death of her husband.
The second condition for a tragic hero is what is called Hamartia, a tragic flaw that causes the downfall of the hero. Blanche's tragic flaw is that she is dependant on men, so much so that she makes choices and does things that are morally questionable. She manipulates and lies to potential suitors to make herself seem more attractive and younger-which in her mind is the only way a man will love her. She does this with Harold "Mitch" Mitchell and it seems to be working until Mitch is informed of all the lies he's been fed, at which point Mitch breaks up with Blanche and leaves her vulnerable for Stanley to rape.
The reversal of fortune, peripeteia, is when the fortunate hero is down on his luck. In Blanche's case, she loses Belle Reve, her husband is a homosexual and dead, she is evicted from her own town and is losing her beauty. She used to be a wealthy and beautiful Southern belle with a loving family and kind husband but her luck changed