你又没胸凶什么凶
[nĭ yòu méi xiōng xiōng shén me xiōng]
'You Have No Chest So Why Act Tough/Scary?'. Using a play on words involving 'no chest'(mei xiong: 没胸) which sounds like it can mean 'don't bully/intimidate', the person criticizes someone for acting overly aggressive despite lacking the means - either physical attributes or genuine reason - to do so. There is also cultural nuance since Chinese society may associate breasts with attractiveness or strength for females.