Richard "Dick" Grayson grew up as part of a circus troupe called The Flying Graysons, who always astounded the audience with their high-flying acrobatics. However, an assassination by the Zuccos gang sent them falling to their doom. As such, Dick went into orphanage, and he was soon adopted by Bruce Wayne. Later revealing to him his secret identity, Dick followed in the footsteps of Batman by becoming his sidekick, Robin. Years later, Robin would become his own person, founding the Teen Titans and changing his name into Nightwing, after a Kryptonian legend. This would open up the doors to other people becoming Robin, as well as being the new definitive identity for Dick.

The Primeverse version of Nightwing should emulate the performance of Troy Baker in the first Injustice game. But for the Injustice universe, in a flashback, you will also need to emulate a little bit of Scott Menville's performance as Robin from Teen Titans. It is also essential to understand that Nightwing is more jovial than Batman, as he finally found peace in the arrest of Zucco.