Some characters I define good and evil with, for various reasons.
Kei likes to look at the average person as 'good' for example, it helps to write his muse, and gives him a desire to protect the average person.
Whereas others have no definitions for these terms, there are just people, this helps with empathetic characters for example, such as when I write Nato empathy, and conversely a detached Sera/Raien.
Then darker characters, if we are just talking about intensity, I find it difficult to write physically sadistic things out or read them for that matter, not so much to play out the effects of them, characters can grow through those kinds of experiences quite drastically, but fade to blacks are preferred after a point.
Psychologically my darker Sith can go all day and do some really heart tugging scenarios, as can their lust for a fight (depending on the muse),