Seoul stocks ended nearly unchanged Thursday after paring earlier gains as investors assessed the Federal Reserve’s first interest-rate increase in more than three years. The benchmark Korea Composite Stock Price Index fell 2.56 points, or 0.04%, to 6,715.41. Trading remained choppy, with investors largely staying on the sidelines after the Fed raised its base rate by a quarter of a percentage point. The Korean won weakened against the U.S. dollar.