Geeking Down To The Facts: Green Lantern Kryptonite
Lets start with what the Green Lanterns abilities are. The Green Lantern has the ability to construct solid objects with his magical ring as long as his will is strong enough. Basically the power is based on the imagination of the holder of the ring. You think of a giant fist you get a giant green fist... simple enough? Then obviously it should be easy enough for the Green Lantern to imagine Kryptonite and use it against Superman.
There is one problem... does the simple task of thinking of a green rock give it the ability to harm Superman. If the Green Lantern constructed a glass of water and you drank it would it quench your thirst? Do the physical properties of these constructed elements take effect?
This is where I said "fuck it how the shitty fucking balls am I supposed to figure that out?" I have now moved onto plan B. Research. I am like 70% sure that Green Lantern and Superman had to duke it out at least once and I was right. Now it was not the real Green Lantern that is seen fighting Superman here but some one who had stolen another Green Lanterns ring and used it to create Kryptonite. Now this was in the olden days of DC comics where the only weakness to the Green Lantern was the color yellow ... LMFAO.
So all Superman did was turn his cape with the little yellow in it toward the Kryptonite and stopped its affect. So in this comic here it is possible for a Green Lantern to make working Kryptonite but this was in the old days and alot has changed since so I decided to go more recent. So in the comic Man of Tomorrow # 19 the Green Lantern, Kyle Rayner, had the chemical compound of Kryptonite imprinted into his head by Martian Manhunter telepathically in order to take down a rogue Superman. It had worked but he was taken down by Superman bots. To let you know how close he was to taking out Superman...There was a tear in the Green Lanterns eye so HOLD DAT SON!!!
So to my understanding as long as the Green Lantern has the will power and understanding of the workings of Kryptonite he can create a synthetic version which would work on Superman. So suck on that one ... Geek question SHITTED ON!!!