In my book, there is a character, Kalona who is portrayed to be pure evil. All the other characters don't want to mess around with him because he is so dangerous. He doesn't seem to care about anybody, and I think that is what makes him so dangerous. If you don't care about anyone, then you have nothing to be afraid of, because you won't ever have to risk hurting somebody that you love.
I find it hard to believe that it is possible for anyone, in a book, or actually alive to have no feeling or remorse, or good inside them. How can you possibly never feel bad for somebody? I think it is absolutely impossible. I think that Kalona only seems to have no good inside of him because the situations he has been in haven't had the means to cause him remorse, or to feel badly about any of his actions.
I think that if he were in a situation where he actually had a connection to a person and/or what they were going through, and what they were feeling, then he might show his supposedly non-existant good side. This is what makes Kalona so powerful, there is no way to black mail him, or negogiate, because there is nothing that anyone can hold against him. If someone can find a way to connect to him, to get inside of him, and therefore be able to destroy him from the inside out. Then he could be defeated.
