Catholic Catechism Question

The idea that, "the end does not justify the means", is a very true statement to me. A person should not be able to do wrong and say because it did one good thing that it was the right thing to do. Going to an extreme for this hypothetical if a Nazi scientist killed and experimented on Jewish prisoners and then cured polio would it still be ethically correct? Which most people would say no while others may say yes because it cured their polio. It depends on what your own personal beliefs. The loving your neighbor as yourself fits in with this because we all have rights and dignity we should not try to use each other as a means to an end. I would say that, "the end does not justify the means", is an ethical problem in the sense that not everyone follows it. An example of this would be the scientists in the Henrietta Lacks books which would be their making millions by using her cells to cure disease by stealing them and not giving back to her family or telling Henrietta her cells had been taken. I'm not sure if there is a solution to making sure that people follow this rule/statement other than making some law that prohibits certain actions so that the end isn't found through unjustifiable means.