valiant
adjective uk/ˈvæl.i.ənt/ us/ˈvæl.i.ənt/
英勇的，勇猛的;果敢的
very brave or bravely determined, especially when things are difficult or the situation gives no cause for hope
The company has made a valiant effort/attempt in the last two years to make itself more efficient. 公司在过去两年里为提高效率进行了不懈的努力／大胆的尝试。