Black and White

[Ofnuts]

Mostly a matter of adding contrast after desaturation (Color ➤ Desaturate). For this you can use the Brightness-Contrast tool or, for a finer control, the Curves tool with a S shape:

   

However:

• As always, not all pictures work well for this. Professional artists don't take a random picture on the internet to apply an effect on it. They take a picture knowing what effect they will apply later.
  
• Nothing says you can apply the sae setting on the whole image. In the exemple above the area around the eyes would need to be pushed a bit to avoid the shadows.