[Rain Man]

Item 3: A war producing 20 million deaths.

I voted no on this one.

To produce 20 million deaths, I think you have to have two big combatants going all out and throwing haymakers at each other. Unless someone launches nukes, we're talking about a sustained war that involves divisions and lots of people in uniforms and tanks and planes.

First, I think that type of war is going out of style. It's expensive and generally unpopular. It's better to find some angry minority group and arm them, or do cyberwar on their infrastructure, or stuff like that. I don't think anybody wants to get into a big massive land war these days.

Second, there aren't a lot of candidates for a war that produces 20 million casualties. At that scale, I can probably name the only real candidates:

India vs. Pakistan
Russia versus Ukraine or other former Soviet Republic
Russia versus China
Russia versus NATO
Iran versus somebody, but I don't know who. Maybe whatever Iraq becomes.

That said, there are other possibilities, such as:

Israel gets pushed to the wall and nukes most of the surrounding countries
Maybe Nigeria or Burma or Ethiopia gets into a really protracted fight against a neighbor.

The most likely probability would be some very long and protracted civil war in some big third-world country that goes on for 20 years and kills a bunch of people each year. But it would take a really big country to lose 20 million internally. Maybe Nigeria or Vietnam or Mexico with the drug wars. But there aren't that many countries that could lose 20 million without something unprecedented happening.

I think it's either a major nuclear war, which I think is unlikely, or a protracted civil war, which isn't likely to happen in a big enough country to produce that many casualties.