Su was special to Kevin, he just didn't usually make a habit of kicking people's arses. Or threatening them at all, really. Maybe in character, if he thought he had to. But as himself? He didn't even really say it in jest. Made jokes about other people kicking his arse, more like.
"I don't know," he said, laughing, which was the truth. He'd just wanted to kiss her, and then the comment had seemed appropriate. "But I can Kevin you again and we can find out."
This time he stepped closer, resting a hand on her cheek, and kissed her properly. It was really nice kissing Su, and he concluded that the kissing part had been the Kevin-ing.