This task requires the System Administrator security role A defined set of privileges. The security role assigned to a user determines which tasks the user can perform and which parts of the user interface the user can view. All users must be assigned at least one security role in order to access the system. or equivalent permissions. More information about specific permissions and performing this task while offline: Configuration Permissions
You can disable a user's record to prevent the user from being able to access Microsoft Dynamics CRM Online. You can only disable a user record, not delete it.