I am adopted and would like to know the percentage of people that don't overcome their past and succumb to the nature of life that they were once exposed to before being adopted i.e. becoming an adult and turning to drugs, chronically breaking the law like their father, and abusing their spouse/children after once being abused and neglected by their own biological family; Not living a healthy, successful life.
While being an adopted child has it's own challenges, I think you're confusing the question by assuming adopted children were abused.
We all have pasts to overcome, some worse than others. And we all rise, or fall, according to our ability to overcome the past. Truth is, there are no percentages out there on who succeeds and who fails with relation to their past.
Attitude plays a part, too. Such as something I read in an Anthony Robbins books a long time ago. Two brothers were interviewed on how they ended up where they are in life. They were the son of a drug dealer felon who spent much of his time in prison and the other time doing things to get himself to prison. One son is in prison. The other son has a good job, happy family, and his own home. When asked about their father's influence in their life, both brothers answered, "What else could I become?"