Well I think you forgot a type.
There's people who do evil, but think they're doing good.
There's people who are doing evil, but for a motive.
And then there's people who are doing evil, but for no reason.
The first is misguided, and perhaps the least scary. The second are calculating, evil, but understandable; A person who is paid to kill other people and makes good money doing it, evil? Certainly, but we can understand their motive and why they do it. And finally the ones who simply does evil for the sake of it. These are possibly the scariest, they aren't misguided, they aren't trying to gain something, they just don't care that what they're doing is bad.
Though evil is subjective, to quote Yahtzee "Even Jeffrey Dahmer wouldn't call himself evil, just misunderstood." Evil is something ambigious and hard to define, and varies from person to person. For my examples just assume killing people - in my personal view human life is the most valuable things we as people have, and thus one of the worst evils.