You're browsing the GameFAQs Message Boards as a guest. Sign Up for free (or Log In if you already have an account) to be able to post messages, change how messages are displayed, and view media in posts.
No, invincibility won't help in duels. It's not hard to win this duel, just pull down and then up really fast, and then wait for the targeting reticle to turn red before marking him. Set several critical hit markers, and you should be able to kill him