I am looking for a way to create an **undeletable admin user** in wordpress. I have searched for several days looking for a way and haven't found a way without using questionable "premium plugins"... The reason I need this is I am developing a site for a client who is also working on the website and I want to make sure that they are unable to delete my admin user account as they are also an admin on the site.

Any help would be greatly appreciated. Has anybody done this before? 

Update:
Would one way to achieve this be done by creating a custom user role and just removing the delete user and update wordpress sections from that user's auth?