Where was this site hosted on? For example, if it is hosted via BlueHost then your ‘Delete Site’ option would not be visible under tools like WordPress[dot]com’s Dashboard.
For Bluehost hosted site, please login to your Bluehost account and follow the below steps:
1. Login to Bluehost and then click My Sites on the Side Panel Navigation Bar.
2. Hover over your Website and click Manage Site.
3. Go to Settings tab and by scrolling down to the end of the page, you will find Delete Site.