The undeal of the year was the termination in January of a proposed buyout of Huntsman Corp. by Hexion Specialty Chemicals, owned by Apollo Global Management. It may be the most expensive case of buyer's remorse ever. Apollo/Hexion, along with banks that were supposed to underwrite the financing, sued to back out of the deal as credit collapsed. But Huntsman, a diversified chemical producer, stuck it to them: the company got $1 billion from Apollo/Hexion for undoing the deal and in June took $1.73 billion in cash and financing from Deutsche Bank and Credit Suisse, the banks that tried to pull the plug.