Doesn’t work with our current understanding of physics.
Hang on I can nerd this harder. It could sort of work if it’s a data signal that exists as noise which disrupts the nervous system of a Superman, but is ignored by the nervous system of a Human.
Must be super radioactive…
Should kill every human in the area instantly
Counterpoint: What if Superman has an element in his body that is crucial to his makeup that is specifically destroyed/harmed by the radioactivity, while that radioactivity passes harmlessly through any other element?An anti-krypton element of sorts, if you will.
Krypton, for example, could be emitting a wave with incredibly low amplitude, but incredibly high frequency. This combination would struggle to make contact with the atoms in normally-dense objects here on Earth, but would strike an ultra-dense object like anti-krypton like a truck.
Too has two O’s because “them, and me too!” There’s two of us!
To has one O because “I’m going TO DO this!” It looks like do!