how do I delete all of my email filter rules at once?

Thank you for your feedback, m.dabio - To delete email filter rules in Xfinity, you can go to the Mail Filter Rules page and click the trash icon next to the filter you want to delete. You can also use the Edit option to modify the filter rules or Disable to turn it off. You can set up and delete email filters individually. 
Set email filters or spam filters — Xfinity Email help