There are 2 approaches to get something equivalent to what you want, but, it isn’t possible to have exactly what you want. On a single site administrator is the highest level, so you can’t have higher than the highest.
Instead, here are alternatives:
- Turn your site into a multisite install that contains only 1 site, and declare yourself super-admin. Other admins will be able to remove you from that site, but you are a super admin, you do not need a role on the site in order to administer it, and they would need super admin rights to administer it
- Create a new user role that can do almost everything the admin role can, but isn’t
- Add code that prevents users with the admin role being deleted, so nobody can delete admins, then use alternative means such as WP CLI to do it
Fundamentally, if you’re concerned these other users might delete your admin user, then this is not a technical problem, but a business problem. The real solution lays in contracts and management. If these admin users are the client, then they’re within their rights to evict you if they’ve paid their bills, either way, it’s not a technical problem. Having this problem is usually a sign that something else has been done incorrectly, e.g. hiring a subcontractor to do dev work but making them do it via the edit theme page in WP-Admin rather than using version control or SFTP.