You don't know Izaya? How can that even be possible? [link] He's one pretty psychotic guy who plays with others' feelings and stays usually on the background. Watch an episode or two (link) and be surprised...
I don't think Light is evil. He makes bad choices and becomes a crazy psycho murderer, but in the beginning he started doing it all for "good reasons". He thought he was doing the right things and the notebook and everything made him go mad. That's not evil to me - just crazy and psycho.
Idk who Izaya is but all those other guys are pretty fucked up. Light started out with good intentions but then was corrupted by all the power and became evil. He's an example of how horrible humanity can become. Then Aizen was a manipulative bitchface who had no conscience and uses people with the promise of power then destroys them once they are no more use to him. And he's also an amazing actor, I mean look how much he fucked up that girl who used to be his co-captain! Orochimaru was just sick and sadistic. Madara used to people so that he could have the most power in the world and control everyone.
All of these guys are manipulative and sadistic and want the ultimate power. Some are actors and others flaunt their evilness. I can't decide. But I would say that compared to the rest Light is the least fucked up. Damn that is saying something about how twisted these other guys are.