[creamyhorror]

"Seven at One Blow" is certainly not a proverb that everyone knows in English; it's the name of the fairytale in English, but not something that people use to mean "bamboozle".

It's simply the case that Chinese relies far more on literary/historical allusions (chengyu) than English does. We might talk about someone's "Achilles heel" or a "Trojan horse", but these literary/historical allusions are simply nowhere near as common as chengyu in Chinese.