The best picks globally to counter Xin Zhao include Samira, Aphelios, and Kalista. These champions are all great at countering Xin Zhao with win rates over 58%. Even if these Xin Zhao counter picks are not picked in the same position as you, it's not a good idea to take him into these matchups. They will most often destroy Xin Zhao.
Yet, if the opposite team brings either Nilah or Irelia, Xin Zhao mains should strongly consider picking him, as he easily destroys these champions with win rates over 53% against both ofthem.