A reminder- Nightblood has a warped definition of evil. From coppermind: "The Breaths it inherited decided "evil was someone who would try to take the sword and use it for evil purposes, selling it, manipulating and extorting others, that sort of thing.""
Szeth doesnt want to do that, he wants to kill the "evil" people who tricked him.
At the very end, with Jasnah- A comment about him finding a woman his age, and there only being one in the area (Cultivation) that wasnt his type.