在战争中，两国士兵成为了彼此的死敌。

During the war, soldiers from both countries became each other's worst ___enemies.

他在商场上树敌太多，现在处处受到排挤。

He has made too many ___enemies in business and now faces opposition everywhere.

糖分是牙齿健康的最大敌人之一。

Sugar is one of the biggest ___enemies of dental health.

这两支篮球队在季后赛中成为了死敌。

The two basketball teams became bitter ___enemies during the playoffs.