A Super Saiyan 10's hair is shorter than a Super Saiyan 9, but is longer than a regular Super Saiyan or Super Saiyan 2. Their entire body is bulky like Recoome's and they are covered from head to toe in hair. Their hair is also grey.
Goku was the first to obtain Super Saiyan 10. He did so while fighting dark DARK TRUNKS while going out of control with power.