Greatest是最棒的 great 的最高级，区别可以从以下例子看出：

Our daughter is great designer, but she said to me she doesn't want to be the greatest one, as that is very hard job and has to sacrifice lot. 我们的女儿是棒的设计师，但她对我说她不想成为最棒的设计师，因为那是一项非常艰苦的工作，必须牺牲很多。