Hi @강민준 • Thank you for reaching out.
This is a lockout scenario. The only option you have is to open a support ticket. They will then engage the Data Protection team, who will require some evidence that will prove your ownership of the Azure Account and unblock you.
You can open a support ticket using the Azure portal as well as by calling at customer service number for your country/region. Also, please go through Manage emergency access accounts in Azure AD to configure a break-glass account so that, going forward, you don't lock yourself out.
Once you are successfully able to login to Azure portal, you will need to delete all users (except the signed-in user) along with the below resources to delete the tenant:
Read more: Delete a tenant in Azure Active Directory
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