Odin tells
In Earth-1610, Thor has multiple hammers which carry the name Mjolnir, and he can wield whichever he deems fit. His original hammer was forged by Odin and carried with it a piece of Asgard so that even if Ragnarök ever took place, Asgard could be reborn.
The hammer was used extensively by Thor as his primary weapon until it was destroyed by Hela in 2017. The broken pieces were eventually made into a tourist attraction in New Asgard.
First was Gullinbursti, a wild boar somehow made in a forge that could both run faster than a horse and glow in the dark. Second was Draupnir, a magic golden ring that would produce nine identical golden rings every nine nights. And third, of course, was Mjolnir, which turned out to be a pretty good hammer.
Chris Hemsworth has five of Thor's hammers and two of his Stormbreakers.
In a compromise, as Bill fairly won the battle, Odin had the Dwarves of Nidavellir create a new hammer made for the cyborg Korbonite warrior, crafted from the same Uru metal as Mjolnir. With the assistance of Eitri and other dwarf blacksmiths, they forged Stormbreaker.
The chemotherapy is attacking the cancerous cells but Mjolnir doesn't identify the cancer as an illness just as another part of her it needs to protect. Plus chemotherapy really does weaken Jane and make her sick so it's easy to see as an illness on it's own.
Other than Thor and Odin, certain other individuals have proven worthy of lifting Mjolnir in the primary continuity: Roger "Red" Norvell (a deliberate ruse by Odin) Beta Ray Bill. Buri (also known as Tiwaz, Thor's great-grandfather)
But after watching new Thor in action, he admits that she deserves the mantle. Thor Odinson initially suspects Jane might be this new hero. But he eliminates her from his list of suspects because she is going through chemotherapy for breast cancer, which, he reasons, would make her too weak to fight.
Mjolnir, Thor's primary weapon, is the most easily recognized symbol of the thundering hero. Bestowed with a blessed enchantment, this hammer can only be picked up by those who have been proven worthy of its immense power.
How did Thanos manage to lift Stormbreaker? Thanos was able to lift Stormbreaker because the axe doesn't have worthiness enchantment as Mjlolnir does. Mjolnir is specific when it comes to the wielder's might since the only prerequisite to wielding is that the wielder is “worthy” of its might.
Mjolnir is a hammer, and was enchanted by Thor's father, Odin, so that only those the hammer deemed "worthy" are capable of wielding or even lifting it. Stormbreaker is an axe, and although it does not have such a worthiness enchantment, its power is such that a mere mortal attempting to wield it would be driven mad.
Thor's love, and the power imbued in his oath, was so strong that Mjolnir could defy its death and repair itself to fulfill a promise and help Jane. Perhaps Mjolnir could've even repaired itself all along, but it didn't because it was waiting specifically for Jane.
Absolutely yes. In fact, there are quite a few misconceptions about Thor's abilities. Even Thor himself was unaware in Marvel's Thor: Ragnarok film.
Thor's most famous weapon, Mjolnir, returns in Love And Thunder, but the reason for the hammer coming back wasn't to save the Asgardian prince. Mjolnir made its triumphant return in Thor: Love and Thunder, but it didn't come back for Thor, despite the God of Thunder still being worthy.
Yes, even Spider-Man has been worthy of holding the hammer of Thor.
Avengers: Age Of Ultron Confirmed Iron Man Wasn't Worthy
Tony Stark was the second one to try, even joking about ruling Asgard if he lifted the hammer and what he would do as king, but his always overly-confident attitude quickly changed when he realized he couldn't lift the hammer.
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.
In the comics, she is still suffering from cancer, but is chosen by the hammer Mjolnir after Thor loses the ability to wield it in battle.
In the comics, whenever Foster turned into Mighty Thor, Odinforce would negate any chemotherapy received. Hence, turning back into a human form meant cancer returned aggressively, killing her slowly.
She can only maintain this form while wielding the hammer, and when she puts it down, her mortal form is weaker than the last time. However, where in the comics Mjolnir is specifically targeting her treatment, in Thor: Love and Thunder, each use of Mjolnir drains Jane's mortal energy.
Stormbreaker replaced Mjolnir upon the hammer's destruction in Thor: Ragnarok, and since Infinity War, it has been his weapon of choice.
Surprisingly, Thor gave Stormbreaker to Love in Thor: Love and Thunder. Having been adopted by Thor, Gorr's daughter has seemingly become the new owner of the weapon forged to defeat Thanos in Avengers: Infinity War.
Overall, though, Stormbreaker seems to have the edge over Mjolnir once again. Strong enough to open the Bifrost, reach Eternity, and manipulate storms the same way Mjolnir can, Stormbreaker's powers are greater than that of the mythical hammer.