The top picks outside of lane to counter Skarner include Kog'Maw, Varus, and Lucian. These champs are all great at countering Skarner with high win rates over 61%. Even if these Skarner counter picks are not chosen in your lane, it's not a good idea to choose him into these matchups. They will likely win against Skarner.
Yet, if the other team brings either Volibear or Talon, Skarner mains should strongly think about selecting him, as he easily dominates these selections with win rates over 56% against both ofthem.