Warning! SPOILERS for Young Justice season 4, episode 25.
The final story arc of Young Justice season 4 seemingly borrowed from the original ending of Infinite Crisis. The first Robin, Dick Grayson, had originally been slated to die a heroic death to save the universe, leading to a renewed partnership between the then estranged Superman and Batman. Unfortunately, the death of Dick Grayson in Young Justice, while heroic, did not yield any obvious benefit to make his sacrifice worth the cost of killing off one of DC Comics' most important heroes.
The events of Young Justice season 4, episode 25, «Over and Out,» placed Nightwing amid a group of young heroes who took up the task of guarding a portal leading out of the Phantom Zone. As his allies held the pass, Nightwing went through the portal and emerged into Superman's Fortress of Solitude, where General Zod and his wife, Ursa, were using a special solar array to speed their absorption of yellow sunlight and boost their strength. Nightwing attempted to destroy the super sunbed, but he was crushed to death after Lor-Zod, General Zod's son, collapsed the statue of Superman's parents that Nightwing had been using as cover.
Related: Young Justice Fixes The Story Of The Most Hated Teen Titan
Curiously, Nightwing almost died in a different version of the Fortress of Solitude in the finale of the 2005 comic book miniseries Infinite Crisis. A follow-up to the original Crisis on Infinite Earths, Infinite Crisis restored the idea of the DC Comics multiverse and was meant to usher in a new era of optimism following what is commonly known as the Dark Age of Comics. Opinions differ on how successful Infinite Crisis was in this, particularly given how many heroes were needlessly killed
Read more on screenrant.com