Hi,
I don't think there is a way from ONTAP CLI to delete a folder (which is non-empty), you can list the folder and delete files but not empty directory. In any case, it is NOT recommended from NetApp CLI. Please delete folder/files from the client side.
I think efficient way would be to delete using command line from either Windows or Linux side without enumerating.
For NFS it's not an issue, for CIFS I find it easier to map "share" using SMB to linux client, once you have cifs shares mounted on linux you can use these or any other command (from google) to get rid of large directory.
From linux: (For ex- Deleting folder 'x')
/]# rm -rf /share/directory/x
/]# rsync -a --delete /mnt/empty/ /mnt/share/directory/x
Thanks!