Two-Face is among the top four or five all-time Batman foes, and the men behind the name... Harvey Dent of Earth-One and Harvey Kent of Earth-Two... had very similar early histories and origins.
What we are dissecting today is how their stories carried on past the point when plastic surgery gave their scared faces and psyche a new lease on life. For Kent, it meant he could finally reclaim his romance with sweetheart Gilda, and the two wed.
For Dent, however, for whatever reason he decided not yet to marry his own love. Perhaps it is for that reason he is alone that evening on a street corner when tragedy strikes twice, and once more he is transformed inside and out into Two-Face. His Gilda marries another man, Dave Stevens, who perishes shortly thereafter thanks to the machinations of Moroni... the same crime boss that initially threw a vial of acid at Harvey in the courtroom that originally created Two-Face. Dent would try to reignite his relationship with Gilda under an assumed identity after getting plastic surgery, only the facial repair was only temporary and this accelerated his madness further.
Meanwhile, Kent, himself still had test and trials to overcome, with first his butler Wilkins assuming his identity and trying to frame him, followed by actor Paul Sloane then stage manager George Blake. Thankfully, this occurred after his marriage to Gilda and his reestablished law practice in Gotham City, hence his reputation was kept intact with only one further resurgence of the original Two-Face of Earth-Two in connection to Sloane and the Crime Doctor, which of course Batman fixed in the end!