The idea with the League of the Unaffiliated is that they are going to be developed by the players. Of them, The Witch King does lean the most towards good and desires peace, although he is still a very corrupted individual and struggles to cleanse himself of his past deeds, Ar-Pharazon is basically neutral and wants all the gods dead, and Saruman has the most evil delusions of grandeur and desire to rule Middle Earth through stealing some of the Secret Fire himself.
It really comes down to how people develop them, they are a bit of a wildcard. Obviously they are the weakest contenders in the Dagor Dagorath, having the smallest territory and armies, but they also hold their own because the main forces of Good and Evil expend so much against eachother, they sort of forget about the league.