Trump card

A “trump card” refers to something that gives one person or group the advantage over another, and it is often used as a last resort effort for a person or group to get what they want. FIFA, the international organization that governs soccer, threatened that players in the Super League would not be allowed to play in the World Cup – the ultimate “trump card.” FIFA’s threat gave them the advantage over the players in the Super League, since FIFA knew players would likely never forfeit their right to play in the World Cup. On the last day of the court hearing, the lawyer brought out a surprise witness as his “trump card” to win the case.