unrelenting

US /ˌʌn.rɪˈlen.t̬ɪŋ/
UK /ˌʌn.rɪˈlen.t̬ɪŋ/
1.

ไม่หยุดยั้ง

extremely determined; never becoming weaker or admitting defeat:

:
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She will be remembered as an unrelenting opponent of racial discrimination.