Digressing somewhat...

The leader of a very large country [...] can have a greater positive influence on the world just by being a fraction of a percent nicer than the average person, than the leader of a small country, or a private individual, can have by being an amazing saint

I suspect you mean "...a fraction of a percent nicer than the average candidate for that leadership position."

Though perhaps it should be "...a fraction of a percent nicer than whoever would have otherwise held the position."

Or perhaps not? Perhaps the right comparison is actually between the results of what they did do (take the position and act as nicely as they did) and what they could have done (act more nicely, or less nicely, or abdicate in favor of someone better qualified, or whatever).

I'm genuinely uncertain, here. It's difficult, when comparing actualities to counterfactuals, to establish clear criteria for what counterfactuals to use.