OP - The consensus in philosophical circles that such things such as malignant evil (evil for the sake of evil) doesn't exist. All "evil" is carried out on the basis of selfish desires. But then so are all good deeds carried out on the basis of selfish desires. Thus you can say that neither good nor evil exist, it's merely selfish desire and motivation.
Evil is just a label. And what defines evil is whatever people were propagandized to believe. The most common cited example of modern day layman's is Hitler. He's almost synonymous with evil.
However, what did Hitler want to achieve? He wanted the German people to be the best, to be safe, and to stop the post WWII persecution and degradation of his people. Is that so different than wanting the best for the people around you? Not really, do you treat your neighbors and friends better than strangers on the street? Probably, everyone does and if you didn't that would be pretty terrible to treat a homeless bum better than your sister or brother.
On the flip side, how could someone who killed so many Jews NOT be evil? Well, symbolically the WWII Germans believed the Jews were the ones who caused the suffering of the country. Another analogy would be, what would you do if someone threatened your family?
Really, what Hitler did was no more psychologically divergent than an extension of what most of us would do for our family. He just viewed the entire country as his family, and like any animal, he is protective of his own, and labels any threat as "evil".
Any of us are not so different and I think people fail to see to label him as evil is just our own way of propagating "evil". Don't you think it's quite bizarre we label people as "evil" because we want them to be enemies and they threaten some value we hold dear? Child molesters are "evil"? Murders are "evil", etc etc. But each of those people do things on the basis of motivation. Child molesters have dopmaine receptors associating children with reward. Somehow that got rewired with sexual satisfaction (anyone who studies neurology understands how the amygdala primes the reward system and how often people mistake sexual gratification for rewards in general). I'm not excusing them, merely explaining it. Most murders kill because they feel threatened.
Haven't you ever wanted to hurt someone who said something hurtful to you? Don't you see how someone could turn murderer very easily if something was said?
I could go into greater detail but GEN Y has a short attention span and if I go on, it's going to be a "too long, didn't read" thing.