Dick Grayson is very different from Bruce Wayne: he's optimistic, laid back and very friendly. Juxtaposed against a dark city like Gotham, Nightwing shines like a beacon of light.
When Grayson confronted Gotham City's darkest corners, his beaming optimism was significantly challenged.
Detective Comics #871-881, by Scott Snyder, Jock and Francesco Francavilla explored Dick Grayson's time as Batman. Indeed, with Bruce Wayne recruiting for Batman Incorporated, Dick took up the mantle of The Dark Knight. These eleven issues saw Dick solve some of the darkest cases of his career. Dick's harrowing adventures began with a three-part arc titled "The Black Mirror." During this story, wealthy Gothamites were getting their hands on dangerous super-villain paraphernalia.
Dick traced the equipment back to "The Dealer," a criminal who auctioned off super-villain gadgets to the highest bidder. Going undercover at one of the auctions, Grayson saw just how depraved the people of Gotham can be, proudly owning sinister pieces of Gotham's history. Batman's cover was later blown, and he was subsequently doused with fear gas. The rabid citizens chased after Grayson, who saw them all as wild animals, barely escaping with his life.
Ultimately, however, Batman overcame his fears and confronted The Dealer, who transformed into a giant monster. While Dick won the fight, The Dealer vanished when his plane crashed. The horrific nature of this case shook Grayson to his core. Later on, when Batman and Tim Drake confronted a gang of poachers, Grayson still suffered the effects of the fear gas, indicating how deeply his latest case impacted him.
In the next arc, "Hungry City," a killer whale was left on the floor of a prominent bank. Shockingly, a dead body was found inside the whale. This corpse belonged to Sonia Zucco's assistant. Sonia was the daughter of Tony Zucco, the man who murdered Dick's parents. While Batman chased after criminals such as The Roadrunner and Tiger Shark, this case was also very personal for him. Grayson's history left him uncertain as to Zucco's true allegiances. As it turned out, Sonia had intentionally led Batman to pursue The Roadrunner, even though Tiger Shark was the real culprit of this whole case. Zucco meant for Batman to eliminate both of her enemies, obstructing justice in the process.
Simultaneously, Commissioner Gordon was dealing with the return of his son, James Gordon Jr. Although James was seemingly reformed, a dark history left Gordon largely uncertain. James had sociopathic tendencies that implicated him in murder at a very young age. Eventually, James was revealed to be torturing people and inverting his anti-psychotics to make him even more psychotic than ever. James intended to use this medication to infect an infant nutritional facility.
The parallel storylines of Dick Grayson and Commissioner Gordon eventually converged, as the two heroes were confronted with some of James' most terrifying crimes. Both Grayson and Gordon worked to bring hope to a dark city, despite everything which they saw. For example, Gordon's ex-wife, Barbara, was also attacked, seemingly by the Joker. Yet Grayson discovered, to his shock, that James went after his own mother.
Still, when James kidnapped Barbara Gordon, aka Oracle, Batman and Commissioner Gordon set out to stop him. James revealed that he knew Dick's secret identity and that he worked with The Dealer to shake Dick's hope and empathy for others. Batman didn't waver, however, as he and Gordon stopped James and saved Barbara.
Despite all of the hardship and darkness which he endured, Dick remained hopeful about Gotham's future. After being doused with fear gas, thrown into a car compactor, held in an underwater aquarium and attacked by a childhood friend, Grayson still fought to protect the people he loved, including Barbara. While both Bruce Wayne and Dick Grayson's Batmen fight for Gotham, Grayson's Batman was a much more empathetic, caring crimefighter. This empathy was illustrated in the profound effect which Gotham's darkness had on Grayson. Bruce may not be fazed by some of these heinous crimes, but Dick's inherent faith in others is incredibly strong, making him sensitive to some of Gotham's darker aspects.
Yet Grayson's relationship with other people is also his greatest strength. Throughout the story, Dick worked with Commissioner Gordon step by step, keeping Jim in the loop so they could collaborate on their cases. This especially came in handy when Dick and Gordon confronted James Jr. at the end of the storyline. Dick's Batman also worked with Oracle and Tim Drake, relying on them for help in a way that Bruce normally wouldn't.
Even after facing some of Gotham's darkest corners, Dick Grayson remained a hopeful, empathetic Batman.