But let's face the truth, some parents have done their best and still have the worst versions of children and some parents have done almost nothing for their children but turns out they have the best children out there.

Very crazy stuff.. to me I believe from my own personal experience and what I have observed in others so far, children have their own will and the upbringing from parent only help to sharpen the will to be a good one. Growing up, children eventually still follow their will and might turn out good if the good upbringing from the parents had any strong effect on them.