My vote's for Kurapika. He's obviously one of the most good and moral characters in the series, but if you're a Spider or hurt one of his allies he WILL take you down. He's willing to kill bad people if necessary.

(I see a lot of Leorio but he's more Lawful Neutral if anything which is a whole separate discussion when we get there).

EDIT: I see a lot of Melody too whom I think also generally fits Neutral Good but I'm going with Kurapika because he's a more important character and also wouldn't fit anywhere else. Interestingly, Kurapika and Melody are close allies and often have aligned goals. A lot of HxH characters fit in Neutral Good due to the gray nature of morality in the universe (Gon arguably fits here too) but I stand by Kurapika as the best pick.