You may recall that John the GL engaged in an interstellar sniper duel with a yellow lantern sniper. They had construct rifles and projectiles. Obviously, the projectiles were significantly FTL to be used in real time and the scopes could find targets on the planet in question.
So, the GLC crosses dimensional boundaries (maybe Disney told them that the DC movies are getting killed by the MU movies - haha). They decide to take out the major standard Earth heroes and villains that you find on Marvel Earth. Let's says there are 25 of them. They set up in a near by solar system and open fire. Who in the MU survives the weapon and can retaliate effectively. For this one, no going back in time or dimension jumping. You have to fight it out.