uncomplaining

US /ˌʌn.kəmˈpleɪ.nɪŋ/
UK /ˌʌn.kəmˈpleɪ.nɪŋ/
1.

無怨無悔

willing to do boring or difficult work without complaining or becoming angry:

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The work is boring, but he's always cheerful and uncomplaining.