Evil does not exist on its own. It's simply a word used by humans to indicate some sort of harm. I don't know how anything can be "deeply evil." Sounds metaphysical. "Very harmful" maybe.
I equate evil with victimization. Evil is the strong punching the weak, an adult spanking a child, an adult scolding a child, an adult manipulating a child with praise, drones ending lives, bosses using employees' economic dependence to control them, teachers using systems of reward and punishment such as grades, detentions, and "good job!" stickers to push kids down paths they wouldn't choose on their own, propaganda systematically diminishing opportunities for acting in one's own best interests (not talking about voting); evil is a human or a human system halting, retarding, redirecting the autonomy of another human without an obvious net benefit to the one acted upon.* (For example, if you push someone out of a car's way and they fall to the ground with some minor scrapes, you're replacing a greater loss of autonomy with a lesser one. A non-evil exception.)
On the other hand, if you look inside the human body for evil, things get a lot murkier, for me anyway. The Alice Miller view, which I subscribe to, locates hate in repressed trauma. Example: Adults beat Stalin badly. Stalin the child, unable to confront the life-threatening horror of the truth, takes on the role of his parents in order to survive. "I'm bad, my parents are right" can be allowed into consciousness. "My parents want to kill me" cannot. The pain of Stalin the child disappears from consciousness but remains in the body. The repressed anger is an internalized conflict, internalized evil. Millions die. If we could look inside Stalin, what we'd find is a miserable bastard fighting for psychic survival. Which is not to say he wasn't evil. Of course. The point is that he was evil. The evil was in him. It just wasn't the work of a rational agent.
Non-sociopaths follow the same processes, more or less. Here's a hypothetical: A man is walking down the street. He sees someone his size punching someone much smaller. A number of forces compete to determine his action. Fear that he might get hurt himself. Fear that if he doesn't help, he'll feel like a coward or moral failure. Does he feel genuine empathy with the victim and want to fight off the bully with a similar intensity he'd want to fight off his own victimizer? Whatever he does, he'll always end up taking the least unpleasureable path. Even empathy works this way. It pushes him in the direction of using his body to prevent victimization, an admirable but dangerous move. The empathic person feels good if he intervenes in this case, bad if he doesn't. He's selfish. Every action is selfish in this broad sense. Selfishness is not the problem. Bad selfishness is the problem.
Stalin was acting bad-selfishly. The forces that won the competition to determine his actions were not empathic or rational. If you could talk to Stalin and give him the best explanation possible for why he's evil and why he should stop murdering people, anything that would make him confront the horrible truth is at a severe disadvantage. It would be recast in terms of the narrative he has spent his whole life constructing to protect himself.
I was a socially conservative Catholic until I was 20. Two things changed me. I read the Bible** and took a class called Philosophy of God with a Hegelian Catholic professor. I had something of an epiphany. Cognitive dissonance won. I just couldn't believe the old stuff anymore. My defenses were worn down by ideas. The struggle to believe things my judgment rejected was too much. These days I'm more principled and politically less of a dick, arguably. So where do I get credit? For reading the Bible? Taking that class? I did those things to try to re-affirm my harmful beliefs. It just didn't work out.
Now even if you take the view that most or many or the most important choices are basically like cake versus salad, the thing I know I shouldn't do and the thing I know I should, where I'm a rational subject weighing the naughty against the nice, the complexity of each human life would make it impossible to determine what sort of free choice was involved in the myriad actions in each human life. Which forces were aligned against which, and how powerful they were, what sort of knowledge, this DNA and that environment, how each choice affects the dynamics of future choices. All these factors would change each new cake versus salad choice. All that matters is what real people do, not what a good person would have done in a situation.
Fortunately, these apparent challenges from a basically relativist perspective are not a problem as long as you focus on evil acts. Shredded limbs, rape, and torture are atrocious to anyone whose body has not been put through hell. We all have the same DNA. This is the anchor. The role of choice in Obama's actions is irrelevant and impossible to determine anyway. But we know he's responsible for killing. We know this is evil because our bodies tell us and we listen. We know that he wants to control and dominate and subjugate, etc. To hell with that mass-murderer. I mean the real Obama, not the caricature who's deviously surveying the same world we are and choosing evil.
*Take out the word human and there's a definition of violence. Violence happens when a force halts, retards, redirects the autonomy of another force.
**Some sects raise kids on the Bible. The kids get used to the crazy. Catholicism raises kids to think God loves them as long as they're obedient and to think Jesus is groovy. They don't emphasize the Bible. You have to be really smart to twist the Bible into a love-y message so it needs to be left to experts.