Originally Posted by
Batgrayson
I think they are both right and wrong.
Kare needs to understand that even if she or Superman never turn into villains, there are still people or aliens that could control their minds and actions. Also, there are many Kryptonian who want to conquer Earth.
By the other hand, Lena needs to understand that someone can steal all her kryptonite and use it against Superman and Supergirl. James could have taken it, that means an alien with superpowers or some human with the right tools can also take it, even Lex. Someone can even steal the "recipe" to make kryptonite, or read Lena's mind to find to to make it.
I would like that at the end of the season, Kara travels to the past of Earth-1, before the last crossover, to give Oliver the piece of kryptonite that he used against Overgirl, but also more pieces, just in case of an emergency, as he said.