Hey, in one of my PnP games I had a Lawful Good Paladin serial killer going around. Yes, he was vanquishing evil, and killing what he deemed as evil, all according to his alignment and beliefs but it went against the ideals and values of the party, who themselves had a LG monk, as well as the city government.
Man, that was a kickass fight. In the end the paladin was slain and his holy avenger shattered.