Wufei, the traitor. If that's what you think, then you obviously didn't listen to Endless Waltz. Wufei makes it very clear that the reason why he fought in Mariemeia's army was because he wanted to find justice for himself. Self-exploration, self-discovery. He never did say whether he agreed with Mariemeia, just that he didn't agree with Relena.
Know that a traitor is someone who betrays. Who did Wufei betray? No one; he was always being true to himself. And who are we to criticize someone who is being true to himself whether we agree or not? The most despicable traitor is one who is a traitor to himself. Wufei moved away from that.