it'd be a wonder if... (following a verb phrase that is usually negative)
Definitions (Wiktionary)
particle
it'd be a wonder if ... (following a verb phrase that is usually negative) (syn.) 先怪
你這麼淘氣，媽媽不擔心才怪！
你这么淘气，妈妈不担心才怪！
nǐ zhè me táo qì ， mā ma bù dān xīn cái guài ！ You are such a naughty kid. It'd be surprising if your mum were not worried.
Examples (Wiktionary)
Mandarin
你这么淘气，妈妈不担心才怪！
你這麼淘氣，媽媽不擔心才怪！
nǐ zhè me táo qì ， mā ma bù dān xīn cái guài ！
You are such a naughty kid. It'd be surprising if your mum were not worried.