Nightwing

Dick Grayson was the original Boy Wonder, and he continued to serve as a sidekick to Batman for quite awhile under the guise of Nightwing. He has since moved on and formed his own team of heroes called Young Justice.

Working in Gotham City
During Knightfall, Nightwing tried to call out Bane numerous times on public radio into an open one-on-one fight. Bane never responded to Nightwing's challenges, and would ultimately be defeated by Azrael, not Nightwing.

When Owlman tried to destroy Earth-One, Batman, Nightwing, and Robin were the ones who actually deactivated the implosive device while the Justice League was fighting the Crime Syndacite. After accomplishing this, Nightwing and Robin actually followed Owlman back to Earth-Three. They fought him in his Owl Cave, but were unable to subdue him because the other more powerful members of the Crime Syndacite arrived back from their defeat at the hands of the Justice League in Earth-One, forcing Nightwing and Robin to hide somewhere to avoid getting pummeled. The two managed to eventually use Owlman's machine to return to Earth-One.

When Catman first appeared on the scene in Gotham City as a ruthless vigilante, Nightwing worked on tracking him down while Batman was busy with other things. Nightwing was disgusted by Catman when he saw him torture the son and daughter of a suspected mobster while they were having dinner in an attempt to get him to make a confession regarding his relationship to a killer named False Face who had for unknown reasons been killing off various mobsters. Nightwing interrupted Catman's interrogation, beating him senseless with his escrima sticks and then turning him over to the police. The reasons behind the False Face killings remain unsolved.

When the Joker abducted Adrian Chase's son and took him to his hideout at a rundown amusement park, Nightwing and Robin tracked them down. Chase's son had mentally snapped, and it seemed like he enjoyed being in the Joker's company, desiring to perhaps become his protege. Joker did not have the same feelings, as he held the boy at gunpoint, telling Nightwing and Robin that if they came any closer he'd shoot the kid. Nightwing, perceiving that Joker would not actually kill Chase's son but would instead want him as a sidekick of some sort, quickly told Robin to back off, and the two of them left the building. This would turn out to be a fatal error, as the Joker knocked out Chase's son and quickly left the building through another exit, and then detonated a bomb which destroyed the building, presumably killing Chase's son. The Joker was picked up by the Gotham police officers outside, but he was just as happy either way, while Nightwing and Robin were left awestruck.

Nightwing, Robin, and Batman worked together to take down Chase, now the Vigilante, before he could get revenge on the Joker and other criminals who had greatly affected his life, such as Deathstroke (who had killed his wife and daughter) and Black Mask and his criminal organization, and Deadshot (who had tried to assassinate Chase while he was running for District Attorney).

Young Justice
During the Tabula Rasa storyline, Nightwing finally decided that he had had enough of Batman, choosing to leave Gotham behind and go his own way. Not long after leaving Batman did he reunite with his friend Roy Harper, who Nightwing had first met back when he was Robin and Roy was Speedy, both serving the same role for the ever-competing Batman and Green Arrow.