5 people to save the world.

[Jakensama]

I still say Dr. Manhattan wouldn't help, though. In the comics he just went all Adama on us and teleported to Mars to live in seclusion.

He had just been manipulated into thinking he gave everyone he loved cancer as the culmination of a decade long plot to neutralize him, I doubt our invaders had the prescience to create tachyons to stop him. Anyway I'll just pick the version of him when he was the republican's bitch who single handedly won vietnam and not years later when he was totally disconnected from humanity.

But if that doesn't convince you, fine, Goku from Dragonball Z - he could blow up the moon as a 6 year old and even though the after effects of his solution kill us all they always manage to wish everyone back to life.