Pepper almost smirked. He wanted it harder? Oh she could do harder. "Never challenge me, Mr. Stark.." she purred in his ear, teasing his ass by grabbing it hard and sliding her finger between his cheeks just slightly before she wound up her hand and smacked his ass even harder. It was making him fuck her harder, which was just how she liked it. "Oh god.. right there.. fuck.. you're gonna make me come.. don't stop fucking me.." not that he was going to but hey.