This article contains spoilers for King in Black #4 by Donny Cates & Ryan Stegman.
King in Black proves the X-Men's Jean Grey is Earth's true champion. Knull has come to Earth - the ancient god of the symbiotes, implacably opposed to light and life, and easily the greatest threat the planet's heroes have ever faced. He ruled the cosmos in the days when the universe was young, striving to prevent the evolution of life, even forging a blade that can kill Celestials.
Earth's Mightiest Heroes fell before him.