The Justice League is full of heavy hitters, from an Amazonian princess to an alien with godlike powers, to a Dark Knight, yet surprisingly the most important Justice League member of all is actually just a man with a bow, Green Arrow.
Time after time, the Justice League has been able to fight back super villains and literal tides of darkness trying to destroy either the world or all reality itself. It's clear that every member of the Justice League has an important job to do. Superman is the muscle and global protector, Green Lantern helps with relations with alien races and is a protector on a galactic level, and Batman is the planner. This isn't even to mention Martian Manhunter, Wonder Woman, or the Flash. Everyone has a role to play, and they do it well, which is why it's so surprising that the most important job of all falls to none other than Green Arrow.
Since the Justice League is constantly going up against unbelievably powerful enemies, it's fair to think that eventually some of them might not come back alive. This is especially true in DC Comics' massive crossovers, such as the recent Dark Crisis on Infinite Earths by Joshua Williamson and Daniel Sampere. This reality-shaking event literally starts with the death of the Justice League. When superheroes die it's not unlikely that their secret identity will be revealed to the world. That's exactly what happened to Barry Allen and Hal Jordan, which is exactly why Green Arrow has the most important job in Brad Meltzer and Phil Hester's Green Arrow #17.
Green Arrow Protects Everyone's Identity
When a superhero dies, there's a risk that their identity will end up going public. When Superman died, some people were quick to point out that Clark Kent was suddenly missing. However, due to the sheer number of people who went missing after Superman's fight with Doomsday, he was able to skirt under the radar. The people of Gotham would have noticed the passing of Bruce Wayne when Batman died if Nightwing hadn't worn the cowl in his absence. But other heroes weren't so lucky. When Barry Allen died during Crisis on Infinite Earths, Hal Jordan and Green Arrow tried to destroy his personal belongings, but they weren't fast enough. Barry's identity went public and this put his loved ones in danger.
Later when Hal Jordan died, Green Arrow wasn't going to make the same mistake twice. Oliver snuck into Hal's home and destroyed everything regarding his personal life; pictures of his family and his loved ones, everything was destroyed. Green Arrow says this is a job he'd do for any League member, that if the day came when Bruce or Clark died, he'd do the same for them. "No one wants to talk about it, but it's a reality of the job," Oliver says. "Someone needs to play clean up." In order to protect his own identity, Green Arrow actually enlisted a villain known as the Shade, since in Oliver's own words, "If you wanna find someone who's going to survive you, pick an immortal."
The Justice League is full of the biggest and greatest heroes in the DC Universe, but when one of them falls it's up to one of their smaller members to clean up the mess, which is why Green Arrow has the most important job on the Justice League.