Warning: contains spoilers for Shazam #1!
While Nightwing recently rededicated himself to acting as Blüdhaven’s greatest defender, there was a time when Dick Grayson failed his adoptive city in spectacular fashion. But thanks to a recent bout against the impossibly large and toxic villain Chemo, Nightwing is able to get revenge for his most devastating defeat with help from the Teen Titans and Shazam.
In Shazam #1 by Tim Sheridan and Clayton Henry, the Teen Titans fight Chemo in New York City. As the radioactive terror threatens to detonate and render the entire city uninhabitable, Nightwing and the Teen Titans work to hold it at bay despite its surprisingly huge size. The team gain the upper hand when Shazam - recently taken under Nightwing's wing as a member of the new Roy Harper Academy - lifts the toxic giant off its feet, with Raven dealing the decisive blow when Billy Batson's powers are revealed to be on the fritz.
While Shazam #1 is the first time readers see Chemo and Nightwing trading blows in the new Infinite Frontier era, the duo's beef actually goes back to the days of Infinite Crisis, the first time the Multiverse as a whole was truly threatened. During this event, Nightwing was going after the Secret Society of Supervillains, a collective whose membership included the Joker and Lex Luthor. In retaliation, the Society lashed out against Batman’s ally by dropping Chemo on his adoptive city. Chemo, as the name implies, is a large monster composed almost entirely of toxic chemicals. When the villains dropped Chemo on Blüdhaven, the monster’s outer shell violently, and explosively, ruptured and destroyed the entirety of Blüdhaven in a toxic green haze. Nightwing was devastated as his city was so violently destroyed, especially since he was ultimately powerless to save anyone in it.
Now, in Shazam #1, Nightwing faces Chemo in New York City. Infinite Frontier is merging all DC's past continuity by combining multiple iterations of reality, meaning that while Chemo's attack no longer canonically occurred and Blüdhaven still exists, Nightwing likely remembers the devastation caused in Infinite Crisis. Dick clearly understands how dangerous Chemo is, but hopefully he also takes some satisfaction in leading the Teen Titans and their students to victory, saving civilian lives and disposing of the toxic villain. Having recently returned to Blüdhaven after recovering from amnesia, Nightwing's victory over Chemo is a symbolic win that makes it clear he won't be allowing the tragedies of the past to be repeated.
Chemo obliterated Nightwing's adopted city, and while Blüdhaven may still be standing in current canon, Infinite Crisis remains perhaps the most devastating loss Dick Grayson has ever faced. That he's been able to save New York from a similar fate, and is now using the fortune left to him by Alfred Pennyworth to support those Blüdhaven would otherwise allow to perish, marks a new era for Nightwing - one in which he's defined by the potential heroism of the future, not the failures of the past.