Number 12 on the list: Munou (Incompetence).
From what I know, there are three things that Edward feels the most guilt over: his mother, Alphonse, and Nina. Nina is a three-year-old memory, yeah, but come on--someone he had come to regard as a little sister was fused together with a dog he played with every day by the person who was supposed to love Nina the most of all. And then, on that same day, he finds her blood and guts splattered all over the wall. That would scar pretty damn heavily into his brain, wouldn't you say? Especially since he thought that it was his fault he couldn't protect her.