They say the distance between insanity and genius is measured only by success, I believe you can say the same thing about the distance between good and evil.

There is no one who is completely evil as to lack some goodness in him.

Good at the wrong place and time becomes evil; evil in the right place and time becomes good.

Light can devour the darkness but darkness cannot consume the light.

There was the kind of silence there might have been on the day before Creation.
Adam stood smiling at the two of them, a small figure perfectly poised exactly between Heaven and Hell.
Crowley grabbed Aziraphale's arm. "You know what happened?" he hissed excitedly. "He was left alone! He grew up human! He's not Evil Incarnate or Good Incarnate, he's just...a human incarnate-

Others are not born bad or good... and neither are people, by the way.