How to delete a folder, even in every backups of Time Machine? I just noticed that a folder containing personal documents was still on my main disk. I copied to my personal disk (password protected), but I want to also delete the copies which are stored in the multiple backups that Time Machine has made over the years.

Is this possible?
This functionality is built into Time Machine.

Launch Time Machine. Right click on the folder of choice, and select "Delete All Backups..." from the menu. This will comb through all your backups and delete all traces of that folder and its contents.