Frostfist Strider

• WOTC Official Reminder Textofficial rules
  Ward — Whenever this permanent becomes the target of a spell or ability an opponent controls, counter it unless that player pays [cost].

• WWizards of the Coast2022-09-09
  Official Ruling
  You may choose a creature that is already tapped as the target of Frostfist Strider’s last ability.
• WWizards of the Coast2022-09-09
  Official Ruling
  If a permanent has more than one stun counter on it, only one will be removed each time it would become untapped.
• WWizards of the Coast2022-09-09
  Official Ruling
  Abilities that trigger when a permanent “becomes untapped” won’t trigger if a stun counter is removed instead.
• WWizards of the Coast2022-09-09
  Official Ruling
  If a tapped permanent with a stun counter on it would become untapped, a stun counter will be removed from it instead. This is a replacement effect.
• WWizards of the Coast2022-09-09
  Official Ruling
  Stun counters replace untapping for any reason, including players untapping tapped permanents during their untap steps.
• WWizards of the Coast2022-09-09
  Official Ruling
  If untapping a permanent is part of a cost (such as that of Halo Fountain’s first ability), you may pay that cost by “untapping” a tapped permanent with a stun counter on it. The stun counter will be removed and the creature will remain tapped. However, the cost will still be paid.

Rulings via Scryfall