Could Green Lantern create Kryptonite?
Just thought I’d expand on what /u/gamer4maker has already (most excellently) here:
Short answer yes with an if, long answer no with a but.
Basically pre-Rebirth, if a Green Lantern had enough willpower they could create any energy source known to man, including Kryptonite radiation. Since Geoff Johns took over the Lanternverse things may have changed a little. It’s never been explicitly stated, but it’s never happened, and it appears the rules have been changed.
Anyway, on with my answer!
Pre-Crisis? Sure he can!
I couldn’t find a definite example on whether Golden Age Green Lantern, Alan Scott, could create it but I’m very certain he could. However, seeing as his powers come from magic unlike the rest of the Green Lanterns, that’s not really the best answer.
Flashing forward to the Silver Age, we get Hal Jordan and he totally can create it too. Kryptonite was a dime a dozen asteroids back in these days but there are multiple examples. For a very prominent one, check out this cover to DC Comics Presents #26 (1980). Just to prove it wasn’t just cover art lying about the plot:
…a creature called N’Gom … slays Green Lantern, takes his form and removes his power ring.
N’Gom then pretends to be Hal, hence the cover, but Hal “is not really dead, at the last moment he had used his Power Ring to separate his soul from his body,” because this is a comic book in the 80s. Hal basically manages to contact Superman though, who realises the deception and the two fight:
Compensating for this the N’Gom uses the Power Ring to create a massive chunk of Green Kryptonite that threatens to kill the Man of Steel. Green Lantern then grabs a rock [note, this is Hal as a ghost/soul] and strikes his enemy in the back of the head with it, breaking his concentration and making the Kryptonite disappear. Superman resumes his fight with the N’Gom and beats it senseless.
Now, obviously that tale was from 1980, five years before DC would shake everything up with Crisis On Infinite Earths and reboot lots of origins, powers etc, which leads us to…
Post-Crisis? Um… maybe?
There are lots of people online who seem to think the Green Lanterns could still do this, and lots of speculation too, obviously, within the comic books too with little references here and there. There’s this following scene from Man Of Tomorrow #13 where Kyle achieves this feat after “stealing the formula from Superman’s mind” but it didn’t seem something that was ever mentioned again:
It is a good time to look at how Green Lantern Rings work though!
One of the reasons this idea seems so prevalent is due to the fact that Kryptonite is green and the constructs that a Lantern creates are also green, but that’s not actually where the potential to, possibly, pull this off comes from. Looking at the powers list on the DC wiki:
Energy Constructs: The ring can form constructs of Oan energy. The primary function of the Power Ring is to provide a weapon capable of transforming the wearer’s thoughts into physical constructs through the wearer’s strength of willpower. A Green Lantern can create any particular items or construct that they can imagine as long as they have the willpower necessary to will it into existence. The constructs are made out of bright green energy, which is a tangible form of pure willpower, and they exist only as long as a Green Lantern is fueling it with their willpower. Items created by the rings are not indestructible and are only as powerful as the willpower of the Green Lantern creating them. The types of constructs usually reflects the ring wearer’s personality. For example, Kyle Rayner was an artist, so his constructs reflect his strong imagination. John Stewart is an architect so his constructs often appear mechanical as if he designed them in his mind before making them a reality.
While cool and super powerful, the constructs are just that – they’re constructs. Hal, Kyle, John or whomever could totally create a glowing chunk of green rock that looked just like Kryptonite but it wouldn’t be any more dangerous to Superman than a picture of Kryptonite or an ordinary rock.
However! Another one of the ring’s powers is where this gets more interesting:
Energy Projection: The ring can be used to fire blasts of Oan energy or create weapons such as projectiles of them. The ring can project beams of force powered by the will of the user. The ring can be used to produce kryptonite and kryptonite radiation. Kyle generally used fanciful constructs in the shape of advanced technology. Their appearance does not indicate the power of the weapon. The weapon’s power is more an indication of the will of the user. Certain users (i.e. Hal Jordan) have been powerful enough to stagger even Superman. If the user wishes, they can alter the form of the blasts such as Kilowog’s “booms.”
Now, that thing about actually reproducing Kryptonite actually cites the very issue I linked to above and notes this might not be relevant post-Crisis. That said, the rings have been shown replicating a, seemingly, limitless range of energies over the years, including magnetic, heat, gravitational and more. The idea is that if the Lantern had the knowledge and understanding of the Kryptonite radiation they would be able to replicate this as well – the same theory that leads to the idea of the rings emitting red sun radiation to depower Superman… but that’s probably a whole other post.
In the New 52? Oh man, who knows?
We’ve got even less material to work with than we did for the post-Crisis world but it certainly hasn’t been shown to be something they’re able to to do, just yet. As always, this could in theory change with any new writer every Wednesday when the new books come out, so don’t sue me if Hal/Kyle/John/Baz or anyone else does this next week :)
Anyway, hope this was helpful! – and besides, we all knows Supes would win, regardless, right? ;)