Tā xiàng dàhuīláng yīyàng wēixiǎn, bùyào qīngyì xiāngxìn tā.
He is as dangerous as the big bad wolf — don't trust him easily.
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大灰狼 is the Chinese equivalent of the 'big bad wolf' from Western fairy tales. It is widely used figuratively to describe a predatory or untrustworthy person, especially in warnings to children.
