"I basically get to be a horrifying tyrant because I can! Oh wait, we're gonna try and make it seem OK by having me misunderstand what my father was telling me about my destiny? Still doesn't make sense that I'm basically a sociopath!"
That's not exactly it. Akito wasn't the real villain, the entire Souma family "system" and everyone who supported it and pushed it was the villain. Most of Akito's sociopath behavior stemmed from the God complex she developed, but that complex only came about because basically everyone in her life was telling her that was her purpose in life and no one questioned it at all. When so many people in your life are telling you something and no one else is speaking up to contradict it, of course you'll believe it.
That's why I find it okay that (almost) everyone in the zodiac forgave her, and why I ended up forgiving her too. Of course, I definitely understand why Rin and a lot of the viewers wouldn't be as forgiving. ---