When the game introduced me to a fallen paladin, I expected another Carth. Maybe Aerie. With a lot of whining and frowning. Instead the ex-paladin paid attention and learned from me. At some point he made a choice, inspired by my actions, and accepted an offer to became a champion of Shar, a truly evil and remorseless killer. He was given nice evil armor and an even nicer, evil two-hander. (Alternatively, you can help your ex-paladin to regain his paladinhood). Needless to say, I liked this development a lot. Well done, Ossian.
What I liked even more is that I told him "don't do it" in both cases (the above mentioned choices), but my influence was low and he rejected my opinion, especially since it contradicted with my gameplay choices.