Meteor

The meteor was a giant extraterrestrial rock that fell to Earth and threatened the destruction of Z-City and its surrounding areas. It was assigned a disaster level of Dragon.

Appearance
The meteor was a giant asteroid that glowed upon entering the Earth's atmosphere.

Giant Meteor Arc
Astronomers detect an asteroid heading toward Earth. It suddenly shifts its trajectory and aims for Z-City. All S-Class heroes are called to deal with it but only Bang, Bofoi, and Genos respond. The meteor withstands Bofoi's missiles and Genos's full-powered blast with no apparent damage. Saitama then arrives and shatters the meteor with one punch. Although its momentum is halted, the meteorite fragments scatter across the Z-City and leave it with massive collateral damage. There are no fatal casualties.

Abilities and Powers
The meteor was classified as a Dragon-level threat by the Hero Association, possessing powerful kinetic energy enough to not only wipe out Z-City but other surrounding towns if hit the ground. It was extremely dangerous that all of the S-Class heroes were summoned in order to stop it, although only Bang, Genos and Metal Knight were able to come in time.

If it wasn't for Saitama decreasing its force and lessening the shockwave, the meteor would have blown everything away regardless of whether civilians were hiding in an evacuation shelter or trying to get out of Z-City.

Physical Abilities
Immense Kinetic Energy: The meteor was assigned a threat level of Dragon, which Genos has remarked that it had enough power to completely destroy Z-City and even damage the neighboring cities. Even after Saitama destroyed the main body, its fragments still had enough power to devastate Z-City and leave it in ruins. In the anime, it was marked a 6 to 9 on the Torino scale.

Immense Durability: The meteor was extremely heavy and durable, being able to easily withstand the firepower of Metal Knight's missiles. It was also unaffected by Genos's fully powered incineration blast.

Trivia

 * The reason why no other S-Class heroes were there during the giant meteor incident was because the meteor struck on short notice, and most heroes were too far away to reach it in time (35 min).
 * This is the first categorized disaster level that is not a living being.
 * The meteor was said to earn a 6 to 9 rating on the Torino scale, a real-life scale used to measure the threat of meteorites.
 * It is stated by Genos during the raid on the Monster Association that he is capable of destroying the meteor in a single shot after his Monster Association Arc upgrade.