A loner by nature, Knuckles is independent, headstrong and serious, yet gullible and short-tempered to a fault. He is entirely devoted to his duty, spending most of his time on Angel Island protecting the Master Emerald, and rarely cares for anything that is of no importance. When his friends and others are in need of his help, however, Knuckles can always be relied on being willing to leave his post and prove himself a faithful and good-hearted hero.

As this comic starts right after Sonic Forces, I suggest going for a voice type similar to his VA in said game, Travis Willingham. Here's an example: https://youtu.be/SB7JjClGQcA?t=8m18s