Spoilers here if you haven't finished Kotor 1 (like there's someone here who hasn't )
I have to say that I was pretty disappointed with the way evil was handled in Kotor 1 and I've seen plenty of posts from other people that seem to agree with me. My character seemed more like Malak than Revan. I felt more like a stupid brute rather than the master tactician that won the Mandalorian wars. The only Dark dialogue choice that fit my idea of what an evil, intelligent, and subtle Sith might do would be when you can encourage Zaalbar to kill the slavers who put the Wookie down. That's my idea of a Dark Lord. He would only resort to killing someone himself when he had no other choice instead prefering to subtly control others to carry out his wishes.
I mean what's more evil, killing someone or getting they're best friend to kill them? Obviously the latter, since it might also gain you an ally that you can use to further carry out your goals. Not only that, but you could also betray said friend by going to the authorities. It's more evil to mess with people heads to use them than to outright kill them. Why do something yourself when someone else can do it just as well?
I really hope the dark side is better concieved in the sequel.