The heart is deceitful above all
things, and desperately wicked: who can know it? Jeremiah
17:9
It isn't primarily our genes, parents, surrounding environment or other things that make us bad. It is OUR own heart. We are NOT good people who sometimes do bad things---we are bad people who sometimes do good things.
For from within, out of the heart of men, proceed evil thoughts, adulteries, fornications, murders, Thefts, covetousness, wickedness, deceit, lasciviousness, an evil eye, blasphemy, pride, foolishness: All these evil things come from within, and defile the man. Mark 7:21-23