To delete a calendar from Google:
1. Sign in to your Google Calendar.
2. Click on the dropdown menu of the calendar you'd like to delete.
3. Hit "Calendar Settings" and scroll down to the bottom of the page.
4. Hit "Permanently delete this calendar."
5. Click on the "Yes, I definitely want to permanently delete this calendar for everyone" box.
6. Hit "Delete for everyone."
Here's a demo video on how to delete a calendar from Google: