I suppose the main focus would come down to a morality decision with how things are evil or not evil. PC's/Adventurers are basically just killer hobos who run around and gather the most loot they can while dispatching what is their way, but then again that may not be evil because most of the time it's not just on a whim and they are doing it for a cause or job. With this in place though you could also say that some clerics or even paladins could be evil. not the lawful evil paladins I mean even lawful good. One scenario that was fun to pull on the morality code is to have a theif that maybe had been a contact for the Paladin captured for thievery by the same Paladin's order and is supposed to be executed for it.