Fal 'Chavamee

Fal 'Chavamee was a Sangheili that held the title of Arbiter at some point in the Covenant's past, and is thus the first Arbiter chronologically depicted in canon. The head of his clan, Fal considered the Great Journey to be a lie, for which he was declared a heretic, but not until he started openly questioning the Sangheili's alliance with the Prophets was he declared an enemy of the Covenant. Seeking to save the clan, a servant allowed Haka to gain access to Fal's home, where Haka forced him to kill Han, knowing that this would draw Fal into a confrontation with him. Devastated by the loss of his wife, Fal swiftly moved to take Haka up on the challenge, literally ploughing his way through an entire Covenant army to reach his wife's murderer. Though he was mortally wounded by Haka's blade, he also managed to stab his enemy with his own energy sword, both dying at each other's hands.

Before Fal's actions, the rank of Arbiter was considered a privilege. His heresy would lead to the Prophets declaring the rank of Arbiter to be one without honor, given to those who could be useful to them as a last chance to regain their lost honor before death. It would therefore be fair to say that he was the last honorable Arbiter until Thel 'Vadamee.