💡 Detailed Explanation
"～末（に）" is used to indicate that a final conclusion was reached after a long process or a great deal of effort. It fits best here, as "何度も話し合った" (discussed many times) implies a long process leading to the final decision. "～あげく" is used for negative outcomes. "～うえで" means "after doing X (as a prerequisite)," and "～結果" simply states a cause and effect without the emphasis on a long process.