Brown v. Board of Education was a landmark case in which it was finally proven that segregation in institutions of education was highly unconstitutional, so you could say that that is the greatest effect since it made other schools become open for everyone as well.
The order helped by acquiring wealth to ransom Christians who were taken by Non-Christians during the crusades. Many crusaders were captured and countries had to pay huge amounts of money for them which was often not worth it. The trinity was established to help the crusaders by getting those people home.
This website is really useful! https://www.state.gov/j/drl/hr/
I would have to say the treaty of versiallest because it affected 100,000 German men