1、He is a treacherous friend who will stab you in the back when you least expect it.
他是一个不可信任的朋友，在你最意想不到的时候会背叛你。
2、The road became treacherous after the heavy rain, with slippery surfaces and sharp turns.
大雨过后，道路变得危险，表面很滑，弯道很急。