Removing "all" users from a SharePoint site

How would one efficiently (i.e., automatically/in bulk) remove all users from a SharePoint site? This would include:

• Removing all users from Groups that have access rights within the site
• Removing all users who have been granted permissions directly to a site resource (file, item...)
• Deleting all outstanding Sharing Invitations

We are hoping to archive sites by keeping them in place with only administrative access (Global Admin or Collection Admin). We need to archive a select number of sites within a collection, while keeping others in production. So this request is specific to a site within a collection, and not collections.

Thank you.