tā / dāng chū / bú zhì zhǐ / zhè zhǒng / xíng wéi / rú jīn / yǎng hǔ wéi huàn / hòu huǐ mò jí

他当初不制止这种行为，如今养虎为患，后悔莫及。

He didn't stop this behavior at the time, and now he has nurtured a disaster and regrets it deeply.