You can permanently delete a group (all of the content and users in the group) from the Group Setting screen. Remember this is permanent; it will remove the group, all the content, and will not allow the users access to it anymore.
Delete a Group:
Step 1. Make sure you’re in the group you want to delete.
Step 2. Click or tap the Group Settings option.
Group Settings option.
Step 3. Click or tap the Delete Group option.
Delete Group option.