I'll play devils advocate and say Donald Trump.
Feel free to use this post to either affirm or deny this.
Defining the person with the most power as "the person who can change the world by the largest amount for the better" - which is a very narrow description, I know - I would say Salman bin Abdulaziz Al Saud, the monarch of Saudi Arabia.
Saudi Arabia is the biggest exporter of Wahhabi Islam, the ideology which ISIS and many other terrorist organisations subscribe to throughout the Middle East, Southern Asia, and North Africa.
If they stopped exporting this ideology it would increase the well-being of billions of people over the next generation.
Women's rights would become more readily available in these countries
Terrorist groups would fizzle out and become a minor threat
Homosexuals would not have to fear being thrown off rooftops
Atheists wouldn't be branded terrorists for simply not believing in God
Freedom of speech would be much more free and we wouldn't have to worry about cartoonists being killed for depicting the prophet Muhammed
It would be much easier to bring aid and relief work to North African nations because the workers wouldn't have to fear for their lives and there would be less people stealing the aid
With groups like Boko Haram gone western education and values like free speech and freedom of religion could prosper in African nations.
Other countries could focus more on their own problems rather than attempting to work out how to fix the civil wars that brew in these ones
The lack of civil wars would mean that the people in these countries could focus on economic, infrastructural, and scientific growth
The potential benefits to humanity that could be made by this man if he simply decided that Wahhabi Islam was a bad interpretation of the Quran and the Hadiths are almost endless and would have the same effect on the world, if not a larger effect, than when Christianity became modernized and gave rise to the largely peaceful societies we see in the west today.
Or perhaps I'm being far too ideological and he would just be assassinated right after making his hypothetical announcement.
Last edited by ProfessorNobody ; edited 1 time in total