I need hardly tell you that the work is dangerous.
这工作很危险，这就不用我说了。
It would be dangerous for you to stay here.
你待在这儿不安全。
Seriously though, it could be really dangerous.
不过说实在的，这事说不好真的很危险。
The traffic here is very dangerous for children.
这里的交通对孩子很危险。
You're on dangerous ground if you criticize his family.
你要是批评他的家人可就惹麻烦了。