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The hammer of Thor is known by Marvel fans and casual followers of the character alike as a mighty weapon that only he can lift - but in actuality, anyone is capable of wielding Mjolnir if they use a specific technique.
In the MCU, fans have already seen Captain America and Vision lift Mjolnir, and while Jane is the first person to show her worthiness, there have been several in the comics.
Prior to the enchantment, Mjolnir was nothing more than a plain warhammer made out of Uru; it is the enchantment that Odin places on it which restricts who may lift it. Thus, anyone physically strong enough could have lifted the hammer before it was so enchanted.
Hence, Mjolnir determines worthiness based on Odin's definition of worthiness. However, since Mjolnir also has a conscious being within it, in the form of God Tempest, another likely explanation is that it is God Tempest that determines the worthiness.
If fans wait to see Peter Parker lift and use it in MCU, they may be disappointed. Despite his strong moral sensibility and strength of character, Peter lacks the ruthlessness that destroys all evil. For this slight defect in character, Mjolnir will never find this Spider-Man worthy of it.
Other Marvel characters have lifted Mjolnir not through worthiness but through technicalities such as absorbing Thor's powers, including the Air-Walker, Awesome Android, Magneto, Rogue, Wonder Man, and Doctor Doom.
But what about someone who was mostly out for themselves? Yes, even Spider-Man has been worthy of holding the hammer of Thor.
Thanos didn't lift Mjolnir, Captain America did
With Mjolnir's worthiness enchantment resulted in Thor being able to lift the hammer only if he is considered to be worthy, but likewise, the enchantment is not discriminatory in nature, and anyone who is deemed worthy is able to lift the hammer.
It turns out the secret he was keeping about Tony Stark's parents – that Bucky (Sebastian Stan) was behind their deaths –was weighing on his mind, making him “not completely worthy” of wielding it.
Venom (2020)
During this battle, Venom (Eddie Brock) was given the powers of Captain Universe, and was able to wield the hammer. However, Venom took this advantage a step further by merging Mjolnir with the Silver Surfer's surfboard to create an even greater weapon.
Moon Knight even seized control of Mjolnir as he revealed that the Uru metal of the hammer is just another moon rock. So while Moon Knight couldn't physically wield the hammer, he could command it to obey his will. And that control extended to Khonshu as well.
And Mathaudhu can cite documentary sources to back him up. For example, Marvel – which publishes the Thor comics – issued a “Thor's Hammer” trading card in 1991 that states Mjolnir is made of Uru and weighs precisely 42.3 pounds. That's lighter than a herd of 300 billion mice, much less a herd of 300 billion elephants.
It can unequivocally be said though, that Red Hulk is not worthy to lift Mjolnir. What makes him so dangerous in comparison to his green counterpart is that he is a much more tactical creature. This you might expect, given he's actually General Thaddeus "Thunderbolt" Ross, longtime enemy to the Hulk.
And not only that, their mission is noble enough that it's earned the loyalty of Mjolnir. While it is still Thor's hammer, it won't hurt one of the Panther Kings. It's even revealed that in the past, the first Black Panther actually once wielded the hammer himself, using it in unseen battle to protect the world.
Mjolnir has been manipulated in different ways in Marvel Comics, and many years ago, Iron Man was able to hold the hammer… thanks to zero gravity, meaning that he didn't properly lift it and he would have still not been able to wield it on Earth because he wasn't worthy.
While no one besides Thor has been able to truly wield the awesome might of Stormbreaker, Groot was the very first being to hold this weapon when one of his arms became the handle for the mighty axe.
Thor replaces Mjolnir with Stormbreaker in Avengers: Infinity War, and the new hammer incredibly overpowers the Infinity Gauntlet with all six stones.
The Power of Love — Red Norvell
In this process, however, Red proved himself more than worthy of the power of Thor, because of his noble, obedient, and self-sacrificing nature. So, Odin decided to adopt Red as his own son and gave him his own weapon: War-Hammer, created from the same metal as Mjolnir itself.
Based on all of this, Batman would almost definitely be capable of lifting Thor's hammer and gaining the powers of a Thunder God. The circumstances that would lead him to wield Mjolnir would likely be extreme as he normally prefers to use his own gadgets and skills - but he could do it.
1 Captain America (Steve Rogers)
However, Marvel Studios president Kevin Feige revealed in an AMA (via Reddit) that Steve was actually "always worthy" and was just being polite. This was further evidenced by Thor claiming he "knew it" in Avengers: Endgame when Captain America battled Thanos using the hammer.
Mjolnir was forged by a dwarf named Sindri. While he was creating it, Loki, the trickster fire god, disguised himself as a fly and attempted to interfere with Sindri's work by buzzing around him. As a result, Mjolnir's handle was unusually short.
Odin's “worthiness” enchantment to Mjolnir was made only during the events of the first Thor movie. Thus, Hela being able to handle/wield the Mjolnir before had little to do about her being “worthy.” You could say part of the reason why Odin added the enchantment is to prevent another Hela from using the hammer.
Hela Was Worthy Enough to Destroy Mjolnir
Many people other than Thor have wielded Mjolnir, including his sister Hela. But the impactful scene in Thor: Ragnarok depicts Hela catching Mjolnir in mid-air before then crushing it to pieces. Odin previously told Thor the power of the Uru metal had no equal.