2 sentences for 苦涩 (kǔ​sè — pained)

1. 想起往事，他的心头泛起一丝苦涩。

   xiǎng​qǐ wǎng​shì, tā de xīn​tóu fàn​qǐ yī sī kǔ​sè.

   Thinking of the past, a touch of bitterness arose in his heart.

   Source: Dong Chinese Dictionary

2. 提到那段失败的恋情，他露出了苦涩的微笑。

   tí​dào nà duàn shī​bài de liàn​qíng, tā lù​chū le kǔ​sè de wēi​xiào.

   Mentioning that failed relationship, he gave a bitter smile.

   Source: Dong Chinese Dictionary