This answer comes from the Interconnected community forum. 👌
How do I untag users in bulk? How can I undo my last operation? I added a tag to all my users?
The first option, if there aren't any users who you'd like to keep the tag on, you can delete from People and Company tags.
If there are users that you want to keep tagged with this tag, there's a bit of a workaround you might find helpful — but it does take a couple more steps. For this example, let's call the tag that needs to be removed "Tag X".
Find the users that you want to keep tagged with "Tag X" , and tag them with a new tag, which we'll call "Tag Y". If there are more than a few users, it's easiest to do this with a CSV import.
Once you've tagged these users with "Tag Y" you can delete "Tag X", then rename "Tag Y" to "Tag x".
You could also get the entire list of contacts here and then remove each contact from being tagged. The only additional information you'd need to make that work would be the tag_id which they can find by getting all tags and searching for that tag by name so you can get the id.
Alternatively, if you use series, create a series where the entry rule is "Tag is Tag X" then add an action to remove the same tag. 👍