Obviously not as cool as Yellowstone going, but I think something like a superbug would really bring out the worst in people, which would be fun to watch.
I'd like to think we'd come together, but after a president getting elected after making fun of a mentally disabled person, people yawning at pictures of Assad gassing children and Puerto Rico, I don't think I can mount a defense.
Tldr: if the Earth’s oceans had twenty times more deuterium than they actually contain, they could be ignited by a 20 million megaton bomb (which is to say, a bomb with the yield equivalent to 200 teratons of TNT, or a bomb 2 million times more powerful than the Tsar Bomba’s full yield). If we assumed that such a weapon had even a fantastically efficient yield-to-weight ratio like 50 kt/kg, that’s still a device that would weigh around a billion metric tons. To put that into perspective, that’s about ten times more mass than all of the concrete of the Three Gorges Dam.
So there you have it — it can be done! You just need to totally change the composition of the oceans and need a nuclear weapon many orders of magnitude more powerful than the gigaton bombs dreamed of by Edward Teller, and then, maybe, you can pull off the cleansing thermonuclear fire experience.