A paper tiger is an expression drawn from a Chinese saying. A paper tiger may pose in a threatening way, but it is actually completely harmless.
A native English expression with a similar meaning is "its bark is worse than its bite," referring to dogs.
Example: Asian politicians and leaders such as Mao Zedong have sometimes referred to the United States as "a paper tiger," describing it as far more menacing in abstract than it would be in reality. Of course, using this description was itself a great deal of political posturing.
Actual paper tigers can be made using origami.