Devil Vs Saint
Some people are very saintly at some times under certain conditions, such as sitting in church, and very devilish at other times, such as tipsy on a bar stool.
Some people tend to be saintly all the time, such as Mother Teresa, and some very devilish all the time, such as a psychopath.
Next I will look at certain personality types and or disorders. If you want me to map out any certain one let me know. Also you can give it a try.