all bark and no bite
纸老虎，嘴上厉害但实际上没什么能耐
口语·形容虚张声势的人
英文释义
someone who talks tough or acts aggressively, but lacks the courage or ability to follow through with their threats or actions
例句
Don't worry about his threats; he's all bark and no bite, just like a yappy little dog.
典故来源
源自狗吠叫却不咬人的现象，比喻人虚张声势而无实际行动。