在辩论赛中，她总是那个最激烈的争辩者，从不轻易让步。

In debates, she's known as the fiercest ___tussler who never gives up easily.

他在拳击场上是个顽强的斗士，从不轻易认输。

He's a relentless ___tussler in the boxing ring, never backing down easily.