In 2018, Thor, Rocket Raccoon, and Groot went to Nidavellir to forge a weapon. Upon arriving, the typically lively forges of Nidavellir were cold and barren, littered with broken parts. Eitri appeared before them and learned that Thor needed a weapon, so he decided to forge Stormbreaker.
Stormbreaker first appears in Avengers: Infinity War (2018)—also the only MCU film in which Thor does not wield Mjolnir at all—and appears again in Avengers: Endgame, and Thor: Love and Thunder.
Although Stormbreaker and Mjolnir have very similar properties and powers, Stormbreaker is the most powerful weapon wielded by Thor so far. The obvious reasons are that Stormbreaker is the physically larger weapon out of the two, and not to mention that it is an axe, which could well be more dangerous than a hammer.
Stormbreaker is imbued with the power of a god who, in theory, would be able to summon the Bifrost. It's a king's weapon, but the mold was not intended for Thor. If weapons were created and imbued at a Gods birth - Mjolnir would be saturated with Death, since it was forged for, and wielded by Hela first and foremost.
Storm breaker is meant to be the strongest weapon of Asgard and could even summon bifrost, says Eitri. But there is no enchantment or spell on it like it was on Mjolnir. So one doesn't have to be worthy to weild it, just the strength to lift it. Clearly Thanos is capable of lifting it.
During a conflict between Beta Ray Bill and Thor, who had been turned into an Herald of Galactus, Bill prevented Mjolnir from returning to its bearer's hand. Seeing no options to reach an agreement, Thor called Stormbreaker and destroyed it by hitting it against Mjolnir.
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.
As Thor described in Infinity War, Stormbreaker was a “Thanos-killing” weapon. Like Mjolnir, Stormbreaker is one of the most powerful weapons in the universe, and both Uru hammers nearly deal killing blows to Thanos in both Infinity War and Avengers: Endgame.
The movie doesn't explain Thor's motivations for giving up Stormbreaker, but it makes sense that Chris Hemsworth simply wanted Love to have a powerful weapon to aid her in battle. It's unlikely that he could give her Mjolnir, considering that so few people in the MCU have been deemed worthy of its power.
How Can Captain America Lift Thor's Hammer? Simple: Steve Rogers is worthy. The inscription on Mjolnir reads “Whosoever holds this hammer, if they be worthy, shall possess the power of Thor.” It doesn't matter how strong you are, if you aren't worthy, you can't lift Thor's hammer, no matter how hard you try.
In the MCU, Stormbreaker was forged by Eitri at the behest of Thor, as a weapon to use against Thanos and his Infinity Gauntlet. In the comics, however, Stormbreaker was still made by Eitri, but pretty much everything else is different.
If Thor decides to use the power of lightning onboard the Asgardian refugee ship to fight the villain and his minions, he may accidentally damage the ship, or worse, even kill his own people. So, he chose to hold himself back, allowing some Asgardians to escape with Valkyrie (Tessa Thompson) and Korg (Taika Waititi).
Unlike Mjolnir, Stormbreaker was never enchanted by the forefathers to only be held by the “worthy”. It was simply a powerfully forged weapon with near-indestructible properties. Cliff G. Anybody can pick up Stormbreaker.
Why couldn't Thor just call back Stormbreaker from the Shadow Realm? He didn't even try, since he knew it was in possession of the God Butcher and he already lost out in the first tussle attempt.
But as it turns out, it was not just Thor's strength. After all, no weapon in existence should be able to stop the combined power of the Infinity Stones, no matter how powerful the wielder is. Turns out, Thanos was taken unawares. He had just incapacitated all the heroes who tried to stop him.
Many viewers have pointed out that Thanos was able to lift Stormbreaker without a problem, but this is because the ax isn't enchanted as Mjolnir is. Others believe Thanos lifted Mjolnir (although briefly) and have even argued that he would be worthy of doing so.
Why does Thor like Mjolnir more than Stormbreaker?
It may be weaker than Stormbreaker in the Marvel Cinematic Universe's lore, but Mjolnir carries the bigger legacy since it holds a deeper meaning to Thor and anyone was worthy enough to wield its power.
Mjolnir has the enchantment where only those who are worthy can wield it, such as Thor or Captain America. Hulk on the other hand, … while Stormbreaker can be wielded by anyone who has the strength to do so (though it can be summoned by those worthy of Mjolnir like Cap did). Case in point, Thanos.
During a Vudu Viewing Party for Avengers: Infinity War, co-directors Anthony and Joe Russo revealed a key difference between Thor's hammer Mjolnir and his new ax Stormbreaker: the latter doesn't require worthiness. That's why Groot was able to lift the ax, not because he was worthy but because he didn't need to be.
It's important to note that the rules around worthiness had been temporarily suspended to allow this to happen. As soon as the fight was over, Superman couldn't lift the hammer anymore. However, under normal circumstances, without any weird interference, Superman is worthy of Mjolnir.
Healing: The axe was able to fully heal Thor and restore his strength when he was badly burned exposing himself to the power of the dying star. Clothes Generation: Stormbreaker is able to conjure various armors such as a viking-like black armor and blue and gold armor.
