To remove the "Unsubscriber" application:

1. Click the gear icon next to the word "Applications" in the lower left hand corner of Yahoo! Mail.
2. Find "Unsubscriber" in the list of applications, and click Remove. (Note: You may have to scroll down to the bottom of the list and click Next.)
3. Click Ok.
4. If the "Unsubscribe" folder is still listed, delete all messages in it, click on the folder, and press Delete on your keyboard.

If you need further assistance with any of these features, please refer to the support site for their developer, Other Inbox.