Mindswipe

• WWizards of the Coast2014-09-20
  Official Ruling
  If the controller of the target spell pays , the spell won’t be countered. Mindswipe will still deal damage to that player.
• WWizards of the Coast2014-09-20
  Official Ruling
  If the target spell is an illegal target as Mindswipe tries to resolve (perhaps because it was countered by another spell or ability), Mindswipe won’t resolve and none of its effects will happen. No damage will be dealt.

Rulings via Scryfall