Who is the best calligrapher of contemporary hard pen calligraphy in China?

There is no best calligrapher.

Everyone's aesthetic taste and ability are different, and everyone's aesthetic requirements and perspectives are also different. Calligraphers only have different levels, and the works of calligraphers with the same level in different periods and different environments are also very different.

For example, the fonts of Qi Gong, Tian Yingzhang, Ren Zheng and Liu Bingsen are all made into standard fonts, and they all have high calligraphy attainments. However, modern people are too familiar with their own fonts, and the level of this aesthetic feeling has decreased. No matter how perfect the computer is, people are tired of it.

In short, what you like is the best! When one day you don't like it, it means that your calligraphy aesthetic ability has improved.