Do spoiled rotten bratty kids always grow up to be spoiled rotten bratty adults? Is there any escape from it or is it inevitable? Why?

not all the time, it depends on the kid

Some do, some don't. Many people shrug off the inadequacy and prejudice of their parents and social environment; many never realise there's a problem. 

I suppose the ultimate case of bad parenting is Ethan Couch "the affluenza teen" but even he could turn into a human being eventually. Unlikely, but possible.