The DC Universe is filled with some of comics' greatest heroes, willing to lay their lives on the line to save just one person, but Batman's greatest fear revealed the Dark Knight as the ultimate hero among his peers. When a villain took a closer look at the biggest fears of the Justice League, Batman showed that the thing that scares him most is not being able to save every person who needs it.
Batman is one of DC's first superheroes, first appearing in Detective Comics #27 back in 1939. While his commitment to being Batman has, at times, ruffled feathers with those closest to him, there's little doubt the Caped Crusader prioritizes saving every person he can. It's part of the reason he refuses to kill even his most sadistic villains. However, Batman is also driven by his greatest fear, as a DC Comics story closely examined what scares him most. The answer: Not being able to be the ultimate hero in the DC Universe by saving everyone who needs help.
In JLA: Classified #14 by Warren Ellis, Butch Guice, David Baron, and Phil Balsman from DC Comics, the Justice League faces off against a machine/monster testing emergent life by showing them their greatest fears. If the Justice League fails the test, the creature threatened to destroy civilization. Superman's greatest fear is losing a fight against a deadly villain and watching it kill Lois Lane. The Flash loses his superspeed at the end of the universe. Wonder Woman struggles to breathe as she sinks to the bottom of the ocean. For Batman, his greatest fear comes in the form of a near-infinite amount of versions of the Joker and his late mother, with the Clown Prince of Crime asking how he could save everyone in the situation.
While Batman would break free from the telepathic takeover, the moment revealed that the Dark Knight's biggest worry is being able to save everyone, even in impossible situations. But, of course, his greatest fear isn't anything new, as Batman's suit has design elements and weapons in place in case it's possible to save even just one life. The trauma of losing his parents and being unable to stop their deaths from happening sent Bruce Wayne on a personal mission to ensure nobody who could be saved died under his watch. Batman's greatest fear proves he's DC's ultimate hero, as he takes on an impossible goal each time he puts on the mask and tries to hold himself to the insane standard.
Batman's obsession with saving everyone is unrivaled by the rest of the Justice League - not that they don't have similar goals in mind. However, Batman's impossible quest to save everyone is his most important mission and a core part of how he acts as a hero, even if it's mainly driven by his greatest fear. Of course, Batman can never live up to his goal, but that doesn't stop him from trying, making him DC's ultimate hero.