I would say that you could find a couple of great quotes that reflect the cruel consequences that Lennie has to face in the last section of the book. The entire discussion with the rabbit and his own projection of fear is a combination of sad and painfully cruel. Lennie's own insecurities are represented in his hallucination and how he has to listen to it. There is a sense of the inescapable, almost as if that consciousness is choking him and constricting him. The voice of Aunt Clara saying what George would say as well as the large rabbit telling him he is not worthy of taking care of the rabbits is painful on a couple of levels. In this instance, Lennie's past and his present converge in a cruel twist, almost indicating to him that his past sins will forever haunt his future. This is cruel because Lennie's childlike hope and sincerity is punctured at such a moment. I would also point to George soothing Lennie with his retelling of the farm and the dreams they share right before he shoots him is another moment of the cruel consequences that await Lennie. I don't think that George is meaning to be cruel to Lennie, but in calming him down by telling him their dream, it is a painful reminder that their dreams will never be realized. Lennie is comforted with a vision that is never to become a reality, pacified by trust and perhaps, recognizing that there ends up being a futility in his being. In this, there is cruelty present, but it is not deliberate on the part of George. Rather, it is the unintentional cruelty that seems to be a part of being human in the setting of the novel.