2 sentences

1. 他虽然工作很辛苦，但从来没有过怨言。

   tā suī​rán gōng​zuò hěn xīn​kǔ, dàn cóng​lái méi​yǒu guo yuàn​yán.

   Although he works very hard, he has never complained.

   Source: Dong Chinese Dictionary

2. 他为这项工作尽心尽力，从未有过怨言。

   tā wèi zhè xiàng gōng​zuò jìn​xīn​jìn​lì, cóng​wèi yǒu guo yuàn​yán.

   He dedicated himself heart and soul to this work and never complained.

   Source: Dong Chinese Dictionary