Are we born just fine and then life happens?
Jeff, what do you mean by "good" and "bad"?
People who grow up to become murderers; stuff like that. Could they have been good kids?
Sure. They could have been relatively good kids. But not every murder is like every other murder.
It's a simplistic question, not just in terms of characterizing people as all good or all bad, but in not recognizing that some murders are easier to justify than others.
No. Of course not. Personality is inborn, and sometimes there is a mismatch between personality and what is expected of us in a particular society or a particular family. The same child might fit in fine in one environment and not another.