Build and Runes
Knock-back/terrain abilities (Janna’s Monsoon, Trundle’s Pillar of Ice) are strong against Skarner because he will have a hard time trying to pull your allies.
Try to break Skarner’s shield as it will remove the bonus movespeed and attack speed that it grants him.
It is imperative that you Flash away when a Skarner is anywhere near you, as you’ll get pulled into the enemy team.
If Skarner is too fast to move away from, invest in a Quicksilver Sash or Mercurial Schimtar to break his suppression and stuns.