What impression does the narrator seek to create by using the adjectives grim, greedy, wrathful, and reckless?

Slim is one of the few guys on the Ranch that tries to Understand George and Lennie. Slim befriends George quickly. He has a sense of fairness and compassion about him. He understands Lennie's mental challenges and knows that, although a large man, he is gentle at heart, "He ain't mean. I can tell a mean guy a mile off." Slim gives George the friendship and conversation that he needs. He also knows that when the mob goes after Lennie, near the end of the book, it would be worse for Lennie to get caught than the alternative.