Just to answer your question properly, I don't think you need to reinstall your PC to get rid of it. Most games are now removing it through an update.

There's a thread on Reddit that collates which games are still using Red Shell and which have removed it: https://www.reddit.com/r/Steam/comments/8pud8b/psa_red_shell...

I think you can just uninstall the ones that aren't planning to remove it yet.

Also, you can opt-out from RedShell's website. Although it doesn't seem straight forward to me: https://redshell.io/optout