the sharp end
noun [ S ] UK informal uk/ˈʃɑːp ˌend/ us/ˈʃɑːrp ˌend/
（工作等的）最难之处，问题多发处
the part of an activity, such as a job, where the most problems are likely to be found
A job like hers would be much too demanding for me, but she enjoys being at the sharp end. 她那样的工作对我来说太困难了，但她喜欢这种激烈的挑战。