Warning! Spoilers for Avengers #33 below.
Mjolnir is an extremely powerful weapon, which is usually only able to be wielded by those deemed worthy thanks to a special enchantment. However, an Avenger just managed to use Thor's trusted hammer against him, embarrassing the Asgardian hero in the process.
Thor's hammer Mjolnir is made from Uru metal and enchanted so the unworthy can't lift it. While other Marvel heroes have lifted Mjolnir in the comics and the MCU, it's rare to see Thor's hammer used against him in a punishing fashion by someone who clearly wasn't worthy. But, in the latest issue of the Avengers, Moon Knight not only used Mjolnir against the God of Thunder but embarrassed him in the process.
In Avengers #33 by Jason Aaron, Javi Garron, Matteo Scalera, and Jason Keith, the Age of Khonshu arc has started, as Moon Knight is taking on the Avengers for reasons that aren't ultimately clear. During his reign, mummies are rising across the Marvel universe. The mystically powered hero uses his own mummy army to take down Doctor Strange, force Black Panther to surrender in Wakanda, and to go for a joy-ride in Ghost-Rider's car. When Thor learns Moon Knight is traveling to Asgard, he attempts to take down the Khonshu-powered rogue Avenger. He throws Mjolnir at Moon Knight, however, he stops the hammer mid-air and throws it back at him.
The scene is not a mirage, as Moon Knight actually embarrasses Thor with his own hammer - but how? Moon Knight explains that he knows Mjolnir is made from the Uru Metal and since Uru is technically moon rock, he's able to control it. Moon Knight repeatedly hits Thor with his own hammer before using Mjolnir to send Thor into space and calling upon moons to come together to crush him. It's an incredibly cool moment that illustrates just how powerful Moon Knight can be, especially when dealing with moon-powered weapons.
Ultimately, it's revealed that Moon Knight took down his fellow Avengers for good reason: He's Earth's last hope against the devil, Khonshu - who's pulling the strings and intends on saving the world in his own twisted ways. Whether Moon Knight is doing all of this in order to gain the upper-hand of Khonshu or he's completely under his control isn't fully clear - but that's par for the course for the character. Rarely are his true intentions known. What is known, is Moon Knight absolutely demolished Thor with his own hammer - a defeat Thor isn't going to soon forget.