Mr. Brownson, I assure you, King's an old enemy of mine.

布朗森先生，我向你保证，金是我的夙敌。

《柯林斯英汉双解大词典》

We are under attack from an old enemy.

某位宿敌正在攻击我们。

youdao

Trust not a new friend nor an old enemy.

新友不可信，宿敌需提防。

youdao

Piracy is an old enemy for the multibillion dollar entertainment industry, the Internet's power to propagate illegal copies notwithstanding.

CNN: Focus on the DeCSS trial

Of the great powers that Vietnam might turn to for friendship, aid and protection, China was an old enemy and the Soviet Union was too preoccupied with its own problems.

ECONOMIST: Nguyen Co Thach

By printing out new cheat sheets as often as every game, teams aren't even vulnerable if an old copy falls into enemy hands.

WSJ: College World Series: College Baseball Showing Signs of a Revolution With Catcher Wristbands