#kryptonite ring

The origin

Superman (1987) #2 (beware the Byrne-era Superman)

(Optional: Action comics annual #1, Adventures of Superman #466, Action Comics #653)

Dark Knight over Metropolis: Superman (1987) #44, Adventures of Superman #467, Action Comics #654

The kryptonite ring first makes its appearance in post-crisis continuity when Lex Luthor fashions a ring from a sliver of kryptonite that came from Metallo. However, its radiation causes him to get cancer and subsequently lose his hand. He keeps the ring in a safe after that. It eventually gets stolen by Amanda McCoy, who has found out that Clark is Superman, and goes to confront him with it. She panics and flees, leaving Clark behind, and she gets mugged and killed. The ring makes its way to the streets of Gotham, where it ends up in Batman's hands.

Dark Knight over Metropolis tells the story of Batman investigating the ring and its previous owner and her death. In the end and after saving each other multiple times, Bruce tells Clark about the ring he found and gives it to him. Eventually Clark shows up at the cave to give it to Bruce, the only man he can trust with his life.

Lost... and retrieved

Superman (1987) #126 (+ optional Action Comics #737)

Superman: Lex 2000

Superman (1987) #168 and Detective Comics #756

In Superman #126, Lex claims he needs the ring when he's on trial. Clark goes to batcave to pick it up himself and hands it over for tests, after which he gets it back, because he believes in fair trial. However, when Clark gets the ring back it's been replaced by a fake (something he doesn't notice because in his Superman blue era he was not susceptible to kryptonite). Luthor has the real one again, right before he becomes president.

panels from Superman (1987) #126

In the Superman: Lex 2000 one-shot, one of the stories shows Batman breaking into Lexcorp to threaten Lex to give back the ring, but this backfires.

panels from Superman: Lex 2000

In Superman #168, Lois then finally decides to take matters into her own hands and asks Batman for help stealing the ring back from Luthor, because Clark won't tresspass into the White House to steal it.

panels from Superman #168

This very chaotic but fun story is continued in Detective Comics #756. In the end, the ring is back with Clark, Lois, and Bruce. Though we never actually see who of them gets to keep it, I'm going to assume it's Bruce, because he has it in Batman: Hush, which takes place some years after this story.

Could Bruce use it? And Batman's paranoia

Superman: The Man of Steel #21

Batman #612

Superman/Batman: the Search for Kryptonite (#44-49) (specifically #49)

Justice League (2011) #19-20

Clark trusts Bruce enough to give him the means to stop him if he ever needs to, but could Bruce actually go through with it if he had to? Now, there are other contingencies that he has for a rogue Superman, as shown in Tower of Babel, but green K is the most direct one.

In 1993's Superman: The Man of Steel #21, set after Superman's death, there is a page that shows Bruce brooding in front of the case where he keeps the ring and contemplates if he could have used it. He sounds doubtful and above all reluctant when he says he would have had to, though ultimately it wouldn't have mattered anymore since Clark was dead at the time.

panels from Superman: The Man of Steel #21

This is much different from the Batman we see in Hush, where he keeps the ring on himself instead of in a case, and uses it without any doubt. In Batman #612, part of the Hush storyline, when Clark is under Poison Ivy's control, he uses it freely on Clark, enough to subdue him and snap him out of Ivy's control, but no more than that.

Of course, Batman doesn't kill, but from the moment Clark gives him the ring, the implication is given that there might be a scenario where it's a last resort and he actually has to stop Clark. I believe there is a comic that explores this in the Armageddon 2001 crossover, but I haven't read it. Or any other Elseworld stories where Superman goes evil, so I'm not aware if Bruce has ever used it like that. I like to think that even if he needs to, Bruce finds another way, because that's what Superman and Batman do.

Finally, in Superman/Batman: The Search for Kryptonite, Clark asks Bruce to help him rid the world of Kryptonite, after the large asteroid that carried Kara had come to earth. They go about this together very meticulously, and in the end, Clark decides to give Bruce the final piece of kryptonite. But when Bruce goes to deposit it in his cave, we see that he has all varieties and a stockpile of green K.

panels from Superman/Batman #49

This first of all is weird because doesn't Clark know that Bruce already has a kryptonite ring? Unless continuity was wiped somewhere inbetween again. But it also shows how paranoid Batman has become, how far we've strain from the Bruce that really trusted Clark and gave him the ring first in 1990 to do with it what he wanted. Instead, Bruce now keeps a lot of kryptonite unbeknownst to Clark. I personally like the 1990 version of Bruce much better.

During the New 52 era, Bruce also had a Kryptonite ring that was given to him by Clark, as shown in Justice League (2011) #19 and #20.

Extra appearances

Superman/Batman (2003) #12, Superman uses it or a different piece himself on Supergirl.

Batman/Superman (2019) Annual 1, a very fun Superman vs. Batman story :D

In animation: Justice League Doom, loosely based on Tower of Babel.