I happen to think the worst evils come from truths, or at least thoughts that the thinker thinks is true.
Take for example the destruction of people committing genocide. They most likely believe that their culture/nation/whathaveyou is better than the other. This is not necessarily a lie, but an incorrect truth. Which would make it not a truth anymore than it is a lie.
I think the undefined term, "evil", comes from the even more difficult to define term, "neutral". As does "good" - as in the opposite of evil. Because there is no action that is unequivocally evil or good in a subjective world. And if the world were a truly objective world, then the words "good" and "evil", in a moral understanding, would be meaningless.
So, like everyone has said before... each word needs to have a solid definition.
