The process is pretty simple. If you know the username and password of the account you want to delete, you can easily delete your account in three steps.
Here’s how:
Log in to the Yandex.mail account you want to delete.
Near the upper-right corner of Yandex.Mail, select your email address and avatar.
Select Account settings from the menu that appears.
Scroll to the bottom of the Account Settings page, and follow the Delete account link.
After clicking the account deletion link, a page will open. We recommend that you read the warnings on this page carefully.
Enter the answer to your security question under Answer. Then enter the security code and delete your account.