To completely remove a tag from your campaign, simply remove this tag from all keywords. The next time the page is refreshed, it will be removed from all places in the platform.
(If you just want to remove a tag from one or more keywords, but still want to use the tag for other keywords in the campaign, follow the instructions here.)
To get started, visit Keyword Settings under Campaign Settings in the left navigation
Click the checkbox at the left corner of the table to select all keywords.
Click Edit Tags and uncheck the box of the tag you want to delete, then click the Apply button.
The tags will be removed from all tracked keywords in the campaign. The tag will be removed from the list and all other places the next time the page is refreshed.