Mill
Issues with the harm principle = overdetermination.
If A were to attempt to stab B and B went to the hospital (due to shock) and found a lottery ticket on the floor, winning a million dollars. This would make them better off. = Risk of harm. Even if they were stabbed, depending on the person, they would be better off. According to the harm principle, person A did nothing wrong, in fact they did something morally correct according to the harm principle.
Or alternatively, A plans to murder B and B finds out. A is locked away but B gets run over by a bus. B is worse off than she was due to A, yet according to the harm principle, A should have never been incarcerated.
Doctors that murder terminally ill patients. - Utilitarian justification via the harm principle for this.