4. Black Mask
The first Black Mask, Roman Sionis, also comes from a prestigious wealthy family, much like Wayne and Elliot. Sionis eventually fell victim to catastrophic failure and embarrassment, namely being dumped by his fiancee and by Wayne Enterprises absorbing his floundering company. Seeking vengeance and redemption, he carved a mask out of his father's ebony coffin which he donned as he turned to a life of crime. Eventually, the coffin mask was burned onto Sionis' face, representing the death of his former life, leaving behind the scarred psyche known as Black Mask.
Why we shouldn't expect them: Black Mask is far from a well-known villain, however he has appeared or been alluded to in many popular Batman texts, including Arkham City. This criminal would have probably worked best as a side-bad guy, much like Falcone or Maroni in Nolan's films. I'd personally love to see Black Mask seek revenge against Wayne Enterprises, but due to his similarities with Hush and his low recognition, I doubt we'll be seeing Sionis anytime soon.