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 all your Duolingo-related accounts!
Your account will be fully deactivated, but you will be able to re-activate it yourself by logging in again.
Be advised that if you are a Duolingo Plus subscriber via the mobile apps, disabling your account will not suspend charges, as those are done by Apple or Google.
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?"