Tā zhēnshì ge bàijiāzǐ, bǎ zǔfù de qián quán huāguāng le.
He's a real wastrel - he spent every penny of his grandfather's money.
Tips
culture
败家子 carries strong moral weight in Chinese - it's not just 'someone who spends a lot' but someone who actively destroys family wealth and reputation built up over generations. The term sits at the heart of Confucian family ethics about preserving 家业 'family enterprise' for descendants.
memory
Read it character-by-character: 败 'ruin' + 家 'family' + 子 'son' = 'family-ruining son'. Once you see this structure you can also recognize 败家女 'wastrel daughter' and the verb 败家 'to ruin one's family'.
