@AtheistDeity,
I'd slow down and take a step back.
Before you delve into the neurochemistry of good and evil, have you truly considered how these words can mean vastly different things?
Take a look at a nice selection of evil from among Nazi war criminals, and you'll see that even among co-conspirators in a single crime, there were many different motives and psychologies:
Amon Goethe -- famous from Fiennes' portrayal of him in Schindler's List. He was the commandant of Plaszow. He was an outright sadist who took pleasure in beating, torturing, and randomly killing people. The same can be said for Josef Mengele, Klaus Barbie, and many others.
Adolf Eichmann -- he was a number cruncher who was the main practical overseer of all the death camps and all the transports of jews from ghettos to the extermination centers. But he was not much of an idealogue -- he was just an obsessive guy who was following orders and trying to do a good job so as to climb in the SS ranks. He'd have done anything they asked.
Rudolf Hoess -- Commandant of Auschwitz -- One of the few Nazis who confessed and apologized before his execution. He oversaw the gassing of between 1 and 2 million Jews in Birkenau. During his testimony at Nuremburg (as a witness against Ernst Kaltenbrunner), he said that he often felt bad for the families he was killing, since he had a family of his own, but he would not ever think of disobeying orders.
Joseph Goebbels, Julius Streicher, Heinrich Himmler -- very different people, but all fully indoctrinated in antisemitic ideology -- this is what motivated them. Goebbels and Streicher were both propagandists (in very different ways), Himmler was head of the SS and the architect of nearly all the Nazis' war crimes and crimes against civilian populations.
Finally, Hermann Goering -- he's the highest Nazi official to sign an order in writing ordering the commencement of the extermination of Jews (though it's known from plenty of testimony that Hitler himself had ordered it). But Goering didn't care much about it -- he was told to sign that order by Hitler, he passed it down, it happened, and he wasn't much involved with it.
What's my point here? It's all the same crime, but the inner motivations were
very different. Goethe loved killing people with his own hands, but his ultimate supervisors (Eichmann and Himmler) both vomited when visiting death camps. Some wanted to inflict pain, some wanted to materialize an ideology, some wanted to advance their careers, and some would just do what they were told.
Are all these things the same, deep down, when one considers neurophysiology? I doubt it.
Evil is the act, not the process.