To disable your entire profile, click on "Deactivate my account" in your settings: https://www.duolingo.com/settings/account
Please be careful as this will disable your whole account!
If someone used your email address to sign up for Duolingo without your consent, please read "Someone created a Duolingo account with my email. How can I remove it and unsubscribe?"
If you need something different related to account removal, please email firstname.lastname@example.org