I was surprised to see Tolian Soran so much in this thread. His primary characteristic was obsession, not malevolence. Not caring that people will suffer and wanting people to suffer are wholly different levels of evil
I can sort of see the argument made for Kivas Fajo, but he's small change really
I might argue it's even more evil to be willing to destroy entire planets if you're mentally capable of feeling remorse.
Knowing the difference between right and wrong and still choosing wrong is worse than not possessing the neural structures to process the concept.