How to permanently delete emails from one sender in Gmail

You can do it by hand, with a filter, with Apps Script, or with a blocker that targets that sender.

Manual

Search from:someone@example.com.
Select all matching conversations (use Select all if Gmail offers it).
Delete, then open Trash and delete forever (or empty Trash).

Also check Spam with the same search.

Filter going forward

Create a filter on that sender with Delete it. New mail goes to Trash. Remember Trash retention.

Automation

Google Apps Script can search Trash/Spam and permanently remove threads on a timer. It works, and you own the maintenance.

Bye is aimed at the same outcome for a block list: while signed in, clear matching senders so you are not babysitting Trash.

Want blocked mail gone without a script? Try BYE! It clears senders you choose from Spam and Trash while signed in, and can one-click clean those folders.

All learnings