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All I remember is a guy who is dying from some kind of radiation, and is trying to find and punish the murderer of his race. He is the last of his kind, and has extreme fighting training, and is one of the best from his race. His race was made up of warriors, and could fight and beat nearly any foe. I think the protagonist was called Keith, or Kyle. He has a ship, and some battle equipment, and, if I remember correctly, a pet of some sort. The enemy was an organization called Darkwing or something similar. I can't remember much more, but I liked the books (it was a series) and really want to find it again!