Steve Rogers aka Captain America has time and again shown that he is a master tactician and perhaps the best fighter in Marvel Comics, and he proves those sentiments true after completely neutralizing Magneto with one genius attack. Magneto is one of the greatest villains in the Marvel Universe as he has been a constant thorn in the side of the X-Men since his debut in X-Men #1. However, the X-Men aren’t the only heroes in Magneto’s crosshairs, and in one single-issue adventure he makes the mistake of tangling with the leader of the Avengers himself, Captain America.
In the mini-comic Captain America & The Incredible Hulk published by Marvel Comics and distributed exclusively to 7-Eleven stores in 1981, Captain America teams up with the Hulk to battle the raging villainy of Magneto. In the issue, Magneto is attempting to get his hands on a rocket so that he could use its destructive powers to obliterate a portion of human society and declare his superiority over those that wish to oppress him and all mutantkind. However, when the combined efforts of these Avengers challenge him, Magneto learns that he never stood a chance.
Captain America was the first on the scene when Magneto stole a rocket because he was asked to be there for the test launch in case anything went awry. Meanwhile, Bruce Banner was in a holding cell nearby after being mistakenly detained but he quickly escapes after transforming into the Hulk. Before the Hulk joins the fight, Captain America is losing terribly to Magneto who is using his powers of magnetism to manipulate the metal all around Captain America and trap him where he stood. When Magneto thinks he has won the day, the Hulk comes out of nowhere and throws both Magneto and Captain America deep into the salt flat desert where there was no metal for Magneto to use against the First Avenger. Using his surroundings to his advantage, Captain America throws salt dust on Magneto which completely neutralizes his powers, making his arrest an easy one.
As explained in the comic, the dust salt worked against Magneto because salt is a non-magnetic solid and when Magneto was covered in the substance he couldn’t summon any amount of natural magnetism around him for his powers to work at all. While it’s unclear if the science behind this defeat was the most sound (though since it happened in a fictional world it doesn’t really have to be), it was clearly enough to work against Magneto and give Captain America a win over the long-time X-Men villain.
While Captain America used his brain to stop Magneto, the Hulk used his brawn to ruin the Master of Magnetism's plans if Captain America failed in stopping him. The Hulk destroyed the rocket Magneto planned to use against humanity while the villain was busy fighting Captain America which ensured that the heroes would win the day no matter the outcome of the one-on-one fight with Magneto. While Hulk’s efforts were valiant and effective, he needn't have worried as Captain America was able to completely neutralize Magneto with one genius attack.