what is it that franek does to get to elie and weaken him into giving up his gold tooth? what emotions causes franek to become so cruel?

Franek begins to torment Eliezer’s father during their marches. The beatings of his father increase until Elie is forced to give Franek his gold crown to stop the beatings. The tooth is extracted with a rusty spoon. Franek must hate himself and be emotionally lost to do such a thing.