It's not hard to decide at all.
Zelgadis, from
Slayers. I'm pretty sure I've addressed why before (old people have a tendency to repeat themselves, you know...) but it's that desperate struggle against self-loathing that gets me. That and his inability to believe that beauty is, in fact, NOT just skin deep -- that Lina, Gourry, Amelia and almost all of the minor characters they meet really DO care about him. And he finally, finally, (albeit grudgingly) admits in the end that he is a good man in spite of it all.
He is the quintessential Hero (if anyone's ever read Joseph Campbell's
Power of Myth or related works you'll know exactly what I mean. He goes into the abyss, right to the edge of "why is it worth living" (why are humans sentient beings, anyway? Why bother? Our lives are so brief!) But rather than destroying it all because he doesn't like it (like a lot of evil or terminally depressed characters do or want to do) he fights back. Life IS worth living and humans ARE worth fighting for, in part
because our lives are so brief and filled with tragedy. And yet we keep on going, and generally strive for the good, the loving and the beautiful.
It struck me right through the heart when I first heard him say "I don't want to lose the man I've become." So ironic and yet so perfect a thing for the chimera -- 1/3 human, 1/3 demon, 1/3 golem -- to say. He may hate his outward appearance, but he is still Zelgadis
And therefore, he is worthy of being alive.
oh yeah... and Kenshin comes in a very, very close 2nd I love everything about him, too... especially that loooonnnng red hair! "The permanent temptation of life is to confuse dreams with reality. The permanent defeat of life comes when dreams are surrendered to reality."
James A. Michener, The Drifters
I came into the anime genre a die hard final fantasy fan, sooooooo.... 
