User blog comment:Skeith9/Heroic Spirits Speculation/@comment-25119196-20140629111230/@comment-24762556-20140630044659

Except no, Arjuna in the myth never used Pashupatastra, after Shiva lend it to him it was just kinda there and was never really discussed on ever again. And yes Karna having lost his armor and Vasavi Shakti before their final duel basically already put him off the list of the people Pashupatastra can be used on.

But even if Karna is in full shape, I doubt Arjuna would want to use Pashupatastra on him. Ever since knowing that Karna is his own half-brother, Arjuna tries to fight as fair and square with Karna as possible on all their duels, even jumping off his chariot for the sake of fighting Karna on foot after he had destroyed Karna's chariot(one could argue that having Krishna as your charioteer already made the fight unfair to begin with but you get the point).

As for the comment about him never fighting Arthur or Heracles, I don't think Hawkeye intended to mean that Arjuna never fought heroes, in the Kurukshetra war Arjuna fought tens of heroes on a daily basis, but what he meant was that there may just be heroes from other countries with methods of countering Gandiva.

Him fighting Shiva under disguise was a one-sided pwnage btw, Shiva was going super-easy on Arjuna and still manages to win effortlessly. The reason Shiva gave Pashupatastra to Arjuna was not because Arjuna passed any tests in battling Shiva but rather because of his devotion for praying to Shiva after he lost. In perspective, Diomedes(the cool one in the Trojan War, not the one with the man eating horses) also punched Ares in the face at one point, but I doubt Ares would actually be anywhere remotely as strong as Shiva.