A Pinch of Powder (PotS #53) states 'After A Pinch of Powder comes out of Shadows, attach it to a character. Limited Response: After you win an Intrigue or Power challenge by 3 or more STR, return the attached character to it's owner's hand. Then, you may kneel 3 influence to return A Pinch of Powder to Shadows. (Limit 1 Limited response per round).

If you play this attachment on a character under the control of another player, who gets to action the Limited Response, the cards owner or the characters controler? Is this the same for attachments that have a way of being moved such as Freezing Rain & Poisoned Wine?

Each card is controlled independantly, so even if you attach the powder to an opponent's character, you still control the powder (and since the powder doesn't change who controls the character, your opponent still controls it), so you're the one who can use the powder's response.

Unless some card effect specifically changes the control of a card, all cards are controlled by their respective owners, and all card abilities may only be triggered by the card's controller (unless otherwise stated on the card).