An S-User is an ID created by the Administrators of your company to allow you access to the SAP Support Portals (like for e.g., SAP for Me). Therefore, in this case to delete this ID you would need to contact one of the Administrators within your company.
To find out who your Super-Administrators are, you can go in the section Users & Contacts > My Important Contacts of SAP for Me (Users & Contacts - SAP for Me) and contact them internally. Alternatively, you can contact the Customer Interaction Center (CIC) and we will be happy to check this information for you.
We hope you found this helpful. Please note that the Customer Interaction Center is available via chat or email and we will be happy to guide you on any of the mentioned processes and assist you with any queries you may have!