当初我怎么没看清你是狗
[dāng chū wŏ zĕn me méi kàn qīng nĭ shì gŏu]
Translated literally as 'Why Didn't I See You Were a Dog Back Then?', it conveys frustration or hindsight regarding realizing someone’s character (often negative traits such as betrayal or ill intentions) too late. It uses animal imagery metaphorically to denote disappointment.