Mistress Rissa is a gentle giantess. She is able to withstand and to put up with things that her fellow giantesses cannot. But even those like her have their limits and this guy pushed her to the wall. She had to push back and she did it by taking him to the woods and crushing the shit out of him and transforming him into a tiny man and making him regret his choices.
Mistress Alexis wanted her slave to understand the powers that she had and what she was willing to do to the loser if he did not act the way she had hoped he would. So the mistress went ahead to crush a toy and then told him that he would suffer the same fate if he did not obey her. He got scared and did not want that to happen to him so he obeyed her.
Mistress Rissa wanted to dominate a loser because she had never done so before. And today she got the chance as she used her giantess fetish to dominate this loser. He had been a nuisance to her and she did not like it. So the mistress crushed him and turned him into a tiny man and made fun of him as he cried and begged her to stop what he was doing to her.