I think every flight instructor has had a student like that at one time or another, my guy was so bad that I lost trust in him. Grounded him and made those endorsements in his log book, he wasn't a happy camper. I went so far at to state in writing in his log book that if he continued to fly the way he did, that he would kill himself and maybe someone else, that he didn't know how to follow rules, "rules didn't apply to him", is how he put it. I made a copy of my last entry in his log book and waited, 22 years later he smoked one in flying VFR into IFR weather, he killed himself and the young women on board with him, not his wife. The family took everybody to court. The insurance companies did a fine job and educated the jury hearing the case. The family got nothing.