[scientizscht (OP)]

Hello

Is there a molecule that kills cells upon contact?

Thanks!

[Bored chemist]

A quartz or diamond crystal (among others) is a single molecule.
If it is big, and going fast enough, it will kill pretty much anything.

[Kryptid]

You mean through chemical reaction? There are many, assuming you aren't limiting yourself to just a single molecule. Fluorine is a particularly nasty one.

[Bored chemist]

If my memory serves me well, it doesn't take many molecules of ricin to kill a cell.

[set fair]

Since it is in this section, I'm assuming you mean kill nasties. If their airborn, propelyne glycol kills most bacteria and some viruses. "Concentrations of 1 gm. of propylene glycol vapor in two to four million cc. of air produced immediate and complete sterilization of air into which pneumococci, streptococci, staphylococci, H. influenzae, and other microorganisms as well as influenza virus had been sprayed." https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2135271/