How to delete all your Telegram contacts at once?
Go to https://web.telegram.org and sign in if you're not already signed in.
On the top-left, click on the hamburger icon to show the dropdown menu, and choose "Contacts" from the list.
Choose "Edit".
Open the Developer Console of your browser (preferably Chrome or Firefox). On Chrome, that is Ctrl + Shift + J.
Run the following JS snippet:
var x = document.getElementsByClassName('contacts_modal_contact')
for (i=0; i