Batman has a history of not getting along with Green Lanterns, but his rivalry with Guy Gardner was nothing more than a joke in the first few issues of Justice League. Despite that, it would come to define Guy's legacy as a character for years to come.
In Justice League #5, Guy decided enough was enough and challenged Batman to a brawl for the leadership of the team. He took off his power ring, got ready to fight-and was swiftly knocked unconscious with a single punch to the face. The fight was over in a single page, and Guy get decked like that was so funny that the rest of the Justice League couldn't resist laughing at his misfortune.
In 1987 writers Keith Giffen, J.M. Dematteis, and artist Kevin Maguire came together to create the Justice League International, a more light-hearted superhero team that combined your standard superhero adventures with the trademark sense of humor Giffen was known for in the industry. The JLI was a team of ten different superheroes that was created to handle threats from around the globe, whereas past versions of the Justice League focused mainly on the US. The JLI's roster included veteran heroes like Shazam, Black Canary, Doctor Fate, and of course Batman, who was appointed leader of the team. Sounds like a pretty solid lineup, right? Well, one person who objected to Batman's inclusion on the team was Guy Gardner, the second Green Lantern of the Earth (or third if you count Alan Scott). Gardner is known for being boisterous and a bit of a meathead, so naturally when Batman was put in charge Guy insisted that he should be the leader instead. That's when the iconic punch occurred.
After regaining consciousness Guy finally learned to accept Batman's leadership role on the team, but he would never live this incident down. The fight-dubbed the "One Punch" by Blue Beetle-would go on to be one of the most infamous running jokes in the superhero community. Apparently, both writers and fans loved the imagery of Batman knocking Guy Gardner out so much that they continue to reference it even 30 years later. But the One Punch isn't just famous in the real world-other DC Comics characters have acknowledged that not only did it happen, but it is incredibly funny. Just a few years after it happened the One Punch was already being referenced in-universe in Green Lantern #25. In this issue, Hal Jordan tries (and fails) to replicate Batman's feat by knocking Guy out with a single blow. And just like the first time, The rest of the Justice League is there to watch it happen and laugh. This isn't just a funny callback, it helps establish that Guy Gardner doesn't get much respect in the superhero community.
Over a decade later In Justice League of America #0, it's revealed that even Superman thinks the One Punch was hilarious. First Batman brags about knocking Guy out to Superman and Wonder Woman, then Diana reveals that Black Canary apparently took pictures of the incident and sent them to her. Batman must have also told rookie Green Lantern Jessica Cruz too because she accidentally admitted as much to Guy while they were training together in Green Lanterns #24. Guy may be a defender of the earth, but being a Green Lantern isn't enough to make people forget you're most embarrassing moment as a Justice Leaguer.
While Guy Gardner may have been on the receiving end of DC Comics' most infamous (and hilarious) one-sided beatdown, he actually holds little resentment for Batman over the incident. Guy can be obnoxious at times but is a hero nonetheless. While it was humiliating for him getting knocked out by Batman was ultimately a good thing for Guy Gardner - not only did it teach him a little bit of humility but it seems like it might have inspired Guy to try knocking people out in one-punch himself. Still, as much as Guy wishes it weren't true, nobody in the DC universe will be forgetting the day he was knocked out cold by Batman any time soon.