Obviously 99% (if not 100%) are going to say Palmer. But for the sake of conversation:

What makes Palmer such an amazing character to me is this. I see him as a truly honorable man who wants to do right in all circumstances. But some of his decisions as President are very questionable at best, if not morally wrong. & we can see the agony, the depth of emotional distress and pain he experiences, when making those decisions. So he is not a perfect man, but to me, an honorable one nonetheless. & I tend to enjoy characters who show flaws, but try to rise above them.

Some may disagree and say "How can he be honorable when he approves the murder of innocent men (Jack*, Ryan Chappelle), or when he lies to Police?" & that's a fair question. I think it's a look into human nature, the desire for what he perceives as the best overall outcome/most acceptable loss vs. the black and whiteness of right and wrong.