Official comment
Hi Justin!
Today, we released Group manager, which includes several features to help you stay organized and keep your data clean.
One of the features in this update includes the ability to bulk delete groups. When you do this, only owners will be able to remove the group from the account completely; the delete action will hide the group from the user's view. I recognize that your request is for the admin ability to delete groups across your account entirely, but I wanted to ensure that you are aware of the new options to clean up.
The new Group manager also includes an owner column for visibility into group ownership.
We are planning on more updates to the Group manager, and we'll update you when they are released.
Learn more about the Group manager here.