How do I delete a iCloud account
How do I suspend a iCloud account I think someone else has been using?
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In case if device is in your possession and your Apple ID is still signed in the device in which secondary authentication was set , convert the account into 2FA If you think your Apple ID has been compromised - Apple Support
You might have revealed account credentials to that person , only an administrator who owe the account can delete the account from server How to delete your Apple ID account - Apple Support