千錘百煉 [－锤－炼]

Jyutping cin1 ceoi4 baak3 lin6
Pinyin qiān chuí bǎi liàn

Definitions (CC-CANTO)
  1. well experienced, after hard works and harsh challenges
Definitions (Wiktionary)
  1. phrase, idiomatic
    hard work and numerous revisions