I don't think hormone tweaking is a humane cure for violence.

Honestly, I don't think I would do anything about violence directly on a patient-level. The incidence of homicide has been steadily falling for centuries. This is a desirable trajectory.

Instead I would seek to improve the socio-economic conditions that I believe precipitate violent behavior. If poor people commit more violent crimes, then we should look for what factor of their condition contributes most to this behavior. I suspect it is the exaggerated boom-bust cycle engendered by living paycheck to paycheck and the disproportional value of status goods in low income communities.

I promote a post-scarcity society as the solution to violent crime. If this proves too distant a solution for your concern, then I would suggest a reform of social services to establish guaranteed housing, food, education, and healthcare through a non-monetary system. I would fund this through taxes and provide the services to even those who do not need them currently. I would attempt to establish these as universal rights that every government should provide on the risk of international sanction.