Please help - this is super frustrating and not intuitive. We no longer need an entire group of contacts and would like them completely deleted from our account without having to remove each individually.
To delete everyone in a group. Go to Audience and click on the name of the group that you want to delete. This will take you to where you can see the Active tab.
In the Active tab you will see directly below it the wording "Active contacts are expected to receive your mailings." Below that you will see the word "Take"
In the drop down next to the word "Take" toggle "selected contacts" to read "all contacts" :
Click the delete button and change "this group" in the drop down to "all group *and* your audience."
That will delete the contacts. Then all you will need to do is delete a group. To do this, simply select the 'Delete this group' option from the dropdown menu to the right of any group name. (To delete multiple groups at once, check the groups and use the main options button in the top-right corner of the audience list. Choose 'Delete selected.')