The answer is Kantian deontology
Virtue-based ethics: It simply means that virtue is acquired through practice. For example, by practicing being brave, generous, kind, honest etc will help in the development of a moral and a honorable character.
Utilitarianism: The theory explains that people should be involved in the actions that foster happiness and the actions that bring about unhappiness or harm should not be engaged in. Utilitarianism is a theory that advocates for a better society.
Conventionalism: This theory explains that the criteria for right and wrong are based on general agreement.
Kantian deontology: It explains morality as doing one's duty by following the rules and regulations without taking into consideration the consequences of such action.
According to this theory, some acts are wrong morally even though such acts are beneficial. Therefore, based on the information given in the question, the answer is Kantian deontology.
In conclusion, the answer is "Kantian deontology.