Nicolas D. Wolfwood from Trigun
I had to think about this one for a long time, but it could only be Wolfwood. If there was ever a maor character that was as complex as the main character himself, I think you know that answer by now. Wolfwood is a man full of contradictions and is two sided, just like every other character in Trigun and Trigun is one of the few series that does this right. He passes himself off as a priest, yet he carries a cross that happens to have a lot of guns in it. He’s a generally nice guy that can have a rough temper. Nicolas constantly challenges Vash’s thoughts of what heroism and they are much better characters for it. Why else would they turn out to be friends and work together well?