The Bronze Age Huntress was Helena Wayne, the daughter of the Batman and Catwoman of Earth-Two, an alternate universe where the Golden Age stories took place. However, she and Power Girl (Superman's cousin on Earth 2) were mysteriously hurled to the main DC Universe after a battle with Darkseid's minions.
Once an upstanding Gotham City district attorney, Harvey Dent was driven insane after a mob boss threw acidic chemicals at him during a trial, hideously scarring the left side of his face. He subsequently adopted the "Two-Face" persona, becoming a criminal obsessed with duality.
For 1988's "Batman: A Death in the Family" storyline, DC Comics held a telephone poll to determine whether or not Robin would die at the hands of the Joker. He was killed off by a margin of 72 votes (5,343 for, 5,271 against). After Jason is killed by the Joker and resurrected in the Lazarus Pit, he goes on to become the Red Hood.