The pain from the subprime crisis has largely worked its way through the investment banking world but might only be just beginning for retail lenders, John Thain, chief executive of Merrill Lynch, said Wednesday. Speaking in Mumbai, he said the credit crunch had taken its toll on consumers and, coupled with rising energy prices and unemployment, could result in higher defaults on retail loans, contributing to weakness in the US economy for at least six to 12 months. Merrill, meanwhile, is targeting the high-growth markets of Asia, where the bank’s operations would be largely unaffected by planned cuts of 4,000 jobs.