This mistress felt that her slave was too slow and she did not want to deal with him in that state. She had to dominate him and she had to make sure he learned to stop being slow. She felt that the best way to dominate as well as humiliate him was to use her faceslapping fetish and that is exactly what she did to him. He learned his lesson the hard way.
Goddess Nemesis wanted to punish this guy and she had to do it because he was insensitive. She did not want to deal with any insensitive asshole and so she had to slap the guy out of his insensitivity. He could not believe how hard and painful her slaps were and he knew he did not want to feel that way again. So he did what he had to do.