Reed Richards designed a weapon so powerful that not only was it made to take down the cosmic juggernaut Galactus, but even Thor would fear the god-killing machine. When Mr. Fantastic's hard drive fell into the wrong hands, Hydra attempted to bring one of his most dangerous inventions to life in Null, a killer android made to eat Gods. While it was designed to stop the Devourer of Worlds, Thor should be equally worried about the creation falling into the wrong hands.
Reed Richards is one of the most brilliant minds in the Marvel Universe, as the Fantastic Four hero has created some incredible inventions with seriously dangerous potential. From a Negative Zone Prison designed to hold heroes who refused to sign up under the Superhero Registration Act in Civil War to The Bridge, which allowed Reed to look into different realities, there's nothing too big or small for the genius-level hero to create. However, in one story, his Galactus-stopping designs fell into the wrong hands, which could decimate gods like Thor if it was constructed.
Related: Marvel Explains Why the Ultimate Nullifier Didn't Kill Reed Richards
In Wolverine #30 by Mark Millar, John Romita Jr., Klaus Janson, Paul Mounts, and VC's Randy Gentile, Wolverine teamed up with S.H.I.E.L.D. to take down some of the most dangerous organizations and weapons in the Marvel Universe. In the arc, Hydra has stolen Reed Richards' hard drive, giving them access to designs to create a potentially world-ending android. Null, no relation to the King in Black's Knull, was initially designed by Mr. Fantastic as a god-killing machine capable of eating gods like Galactus. Wolverine and his team stop Null from being built, but the machine proves Thor and other gods should worry about what Reed Richards can make.
As pointed out in the comic, Null is just one of "eight thousand" ideas on the stolen hard drive. While Thor is a much more powerful hero than Reed Richards in a one-on-one fight, the fact he has designed a god-killing creature capable of taking on Galactus should have Thor and other Marvel gods worried. Besides Null, who knows what else Reed has mocked up?
Thankfully for Thor and other gods in the Marvel Universe, Mr. Fantastic is on the heroes' side. But, when his designs and inventions fall into the wrong hands as they did in Wolverine #30, he becomes one of their biggest threats, even inadvertedly. Reed Richards building an anti-Galactus weapon capable of killing gods can be incredibly useful. Still, for Thor, it represents his own potential destruction and shows that even Marvel's greatest heroes should fear what the Fantastic Four hero's brain can create.