Kryptonite: Use It Or Lose It?

[gkokujin]

How about this?

Lex is introduced to Superman publicly, and he obviously already has a distaste for him and the feeling is probably mutual. For a photo op or something Lex has to shake superman's hand and that's when he notices Superman get weak for some reason and Lex looks at his own hand and recalls his ring is crafted from a meteor rock that was discovered 20-30 years ago.

 

[Ultimatehero]

Not in the first film, but it wouldn't make sense in the first film. Zod can't use it as a weapon. In the second film, with Lex, it definitely has a clear purpose being there.