Ozone is a chemical that can be both friend and foe to human beings - depending on where it is.

臭氧是一种利弊两全的化学物质。是利是弊，这得看它在哪儿出现。

youdao

He believed the Force to be more than just a weapon wielded against a foe.

他相信原力不应仅仅是对抗敌人的武器。

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There will also be a handful of "world" encounters that will require the server to band together and overcome a great foe.

还存在少数的“世界”遭遇战，需要整个服务器联合起来战胜强大的敌人。

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Defense attorneys consider Phillips to be a worthy foe, and he aims to expand his whistleblower business.

FORBES

Setting out precisely who is a friend and who is a foe has often proved to be a shrewd political tactic.

BBC: Why do people keep lists of enemies?

What is already unmistakable, though, is that it is better to be a foe of America than its friend.

CENTERFORSECURITYPOLICY: Obama Doctrine 'coup'