Personaly i dont mind quests where you can show your companions wrong of their way and set them straight ...
Mass Effect did that quite well with some companions.
What pisses me off is that we never get any corruption arcs theese days.
This was quite well done in KotOR II. ... it was just minor detail, and it have zero impact on the story, but i really liked that when you trained your companions to be a jedi, you could instruct them to either focus on tranquility and order ... or destruction and chaos. :3
You want make Astarion good boy? Be my guest ...
But allow me to make Karlach evil aswell ... >:]
Its matter of universal ballance you know?
