Setting method:
realme UI 2.0 & above versions: Settings > User & account > Multiple users> Select the one you want to select > tap on Delete user.
realme UI R & T Edition: Settings > System > Multiple users> Select the one you want to select > tap on Delete user.
realme UI Go & S Edition: Not supported
Note: The Guest account that comes with the system cannot be deleted.
Related Articles:
What is Multi user and how to use it