Answers (2)
Apparently Tungsten? It depends on how you define hardness. While tungsten is extremely hard in its pure state, it is also very brittle. Source: https://bortec.de/en/blog/2017/08/14/the-hardest-metals-in-the-world/
Metals are ductile, not hard. They feel hard to the touch, but being ductile means when you push with a sharp point they will move aside, so a hardness test does not mean much. But as metals go, chromium is the hardest. Here is a nice essay about strength and hardness: www.linkedin.com/pulse/what-strongest-hardest-metals-mike-m-
Here is a comparison of various materials.
www.larsonjewelers.com/Tungsten-Cobalt-and-More-on-Mohs-Scale-of-Mineral-Hardness.aspx