硬骨头

硬骨头:

Literally means:

person of indomitable will difficult task

Actually means:

It figuratively refers to a person or thing that is firm, inflexible or fearless. It is often used to describe person or thing that stands firmly and inexorably against evil. Commendatory.

It means difficult task or hard nut.

比喻坚强不屈或不怕困难的人或事。适用于人或事。常用来指坚决跟坏人坏事斗争，绝对不让步或低头的人或事，并含有赞扬的意思。具有褒义色彩。

比喻难度很大的任务。