That's " to turn on someone" – to suddenly, after being perhaps, being friends with someone, become their enemy.

那就是“攻击某人” ——突然间， 在可能成为某人的朋友之后，成为他们的敌人。

" To turn on" someone means to betray that person – to hurt that person after promising to help him or her.

“To turn on”某人意味着背叛那个人——在承诺帮助他或她之后伤害那个人。

" To turn on someone" means to suddenly change your relationship or your attitude towards another person so that you begin to attack that other person.

“To turn on someone” 意思是突然改变你的关系或你对另一个人的态度， 以至于你开始攻击那个人。