A "subdomain" is part of a "domain". Comes from the same IP and that's all there is. You can deny Google's access (see robots.txt" etc. and also include nofollow noindex meta, etc. but it will be part of your DOMAIN.
The content is either worthy or not. If said content is "pandalized" and you want to remove it, then the best method is TO REMOVE IT, ie. make it disappear, not exist, go away.
There are no magic bullets in subdomains because, like the child, they are part of the parent.