Skullwinder

• WOTC Official Reminder Textofficial rules
  Deathtouch — Any amount of damage this deals to a creature is enough to destroy it.

• WWizards of the Coast2015-11-04
  Official Ruling
  Skullwinder's enters-the-battlefield ability targets only the card in your graveyard. If that card is an illegal target as the ability tries to resolve, the ability won't resolve and none of its effects will happen. No cards will be returned to any player's hand.
• WWizards of the Coast2015-11-04
  Official Ruling
  You choose the opponent as the ability is resolving. You may choose an opponent with no cards in their graveyard.
• WWizards of the Coast2022-06-10
  Official Ruling
  You may choose an opponent with no cards in their graveyard. In that case, they will not get to return anything.
• WWizards of the Coast2022-06-10
  Official Ruling
  The chosen opponent gets to choose which card to return from their graveyard to their hand.
• WWizards of the Coast2022-06-10
  Official Ruling
  Skullwinder's enters-the-battlefield ability targets only the card in your graveyard. If that card is an illegal target as the ability tries to resolve, the ability won't resolve and none of its effects will happen. No cards will be returned to any player's hand.
• WWizards of the Coast2022-06-10
  Official Ruling
  You choose the target card as you put Skullwinder's triggered ability on the stack, but you don't choose an opponent until after you have returned the card to your hand.

Rulings via Scryfall