Sakura and Shirou
The couple both frowned at Locke's statement. Torture really wasn't something they approved of, even on the most foul of enemies. However, they also knew that, in this case, it may well be necessary and, given the creature's nature, they couldn't truly say that they felt much sympathy for it.
Immediately, Nanako moved to obey Locke's instructions, shamelessly flashing her panties as she lifted her leg up high and brought it down straight onto the creature's arms with a loud bang. Sakura winced as she watched the leg crush the creature's bones, causing it to emit a scream of agony, only for the arm to return a moment later, along with the smirk on its face.
Hearing its words and noticing that its arm had regrown, Shirou spoke up.
"Not really", he said. "It's far easier when you don't need to worry about how much damage you cause."
Then, Sakura spoke.
"Are you sure you won't agree to a Geas?" she said. "It would be a lot easier for you that way, and if you do that we won't be forced to destroy you."
"She's right", Shirou added. "What do you have to gain by defying us?"