1, the first step is to show your generosity. Clearly admit this fact, that is to say, he is no longer required to move out, lest they really tear their faces and hurt their feelings.
Step two, the villain is in front and the gentleman is behind. According to the principle of accounting, tell him clearly that he will bear the bulk of the rent, or invite him to eat for a while, or he will bear the responsibility of cleaning, because he broke your agreement first, and he will bear the responsibility for it and make up for your losses. After he agrees, you can be gentle and generous in future actual implementation. This is called agreement to agreement, person to person. If he is not kind, he should not be unjust. Use your generosity to influence him and establish a good image among your classmates.
3. The third step is to establish a sense of vigilance. Judging from your classmate's behavior, this person has a personality problem, at least he loves cheap. You should be careful of such people, and you'd better stay away from him in the future.