To delete a Telegram account, the most immediate way is to use the Telegram account deletion page on a browser:

1. Go to https://my.telegram.org/delete in a web browser.
2. Enter the phone number linked to the Telegram account.
3. You will receive a confirmation code in the Telegram app (not by SMS).
4. Enter the code on the website and click Sign In.
5. Optionally provide a reason for deleting the account.
6. Click "Delete My Account" and confirm by clicking "Yes, delete my account."
7. Your account and all associated data will be permanently deleted.

Alternatively, in the Telegram app, you can set the account to automatically delete after a period of inactivity (from 1 month to 1 year). This deletion happens automatically once the set period passes without logging in. Be aware that once deleted, all messages, contacts, and media are irretrievably lost, and you must wait a few days to register a new account with the same phone number if desired.