BitTorrent seems quite awful from that perspective. For quite a while, torrents required a centralized tracker to coordinate operation, which provided a single point of failure. Even now, with trackerless operation, BitTorrent has no directory or search protocols, no privacy protection or built-in anonymity, and otherwise makes it trivial for anyone to obtain a full list of IP addresses downloading any given torrent.
I wouldn't call BitTorrent "underground" or "difficult to kill" at all. For that, you'd probably want something like Freenet or GNUnet.