Federal regulators and J.P. Morgan Chase – which together managed the collapse of Washington Mutual during the frenzied days of the financial crisis – are embroiled in a fight over who should cover billions of dollars from a legal mess that the failed Seattle thrift left behind. The 2008 implosion of WaMu, as it’s commonly known, was the biggest banking failure in U.S. history, prompting the Federal Deposit Insurance Corp. to take over the firm and then orchestrate a shotgun deal for J.P. Morgan to buy the bank for a paltry $1.9 billion. But the paperwork for the merger was written so hastily over a 48-hour period that it left ambiguous who should cover the cost of WaMu’s liabilities.