Complex sentence: The Patriots, however, were defeated by the New York Giants in Super Bowl XLII, after winning the first 18 games of their 2007 season, and defeated again by the Giants in Super Bowl XLVI.
Split into simpler sentences: The Patriots, however, were defeated by the New York Giants in Super Bowl XLII, after winning the first 18 games of their 2007 season. They were defeated again by the Giants in Super Bowl XLVI.