You missed the main point...if a curse is predicted it CAN be avoided if the person or persons are righteous.
If they are less than righteous than those most likely to inflict evil have to fight the urge to do so.
In the END, your soul must be able to exist fully exposed to God.
What does any of that have to do with your possibility, that the people slaughtered during the holocaust were paying for the sins of a former life? Like what? They ate a cheeseburger? They had sex outside of marriage on the Sabbath?
Are you Buddhist?
Wouldn't such a belief tend to make people indifferent to the suffering of others if they believe that people who are suffering are suffering because they deserve it? Did the tens of millions of people that you say were unjustly persecuted tortured and killed during and since the Inquisition deserve it?
do you think that people with disabilities, or living in poverty, or facing starvation, are guilty of forgotten sins from some unremembered life? What kind of fucked up God would do that? You would worship a God like that?
Isn't it more likely that they aren't guilty of any sin and their suffering is increased if not caused by those who are in good health, well paid, and well fed?