Thor essentially 'gives birth' to Vision, which means there's part of him – or more specifically part of Mjölnir – in Vision, which gives him the ability.
While Vision is, in fact, a machine, Odin's enchantment would likely detect sentience and intentions to judge worthiness, meaning an evil robot like Ultron would not have been able to wield Mjolnir.
A machine can pick up the weapon and move it anywhere since it's mindless and incapable of possessing the morals necessary to be considered worthy. By this logic, Ultron himself could have lifted it, but it wouldn't have done him much good.
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.
The Vision is quite strong as well - he can rip straight through a mutant-hunting Sentinel's armor - but not nearly as strong as Thor. The Vision's only hope in winning this battle rests with his unique ability to control his body's density.
Vision Lifts Thor's Hammer Scene - Avengers: Age of Ultron - Movie Clip HD
Why could Vision carry Thor's hammer?
Thor essentially 'gives birth' to Vision, which means there's part of him – or more specifically part of Mjölnir – in Vision, which gives him the ability.
In the end, Deadpool wasn't worthy. While he seemingly had control of Mjolnir and the strength of Thor, it was all a mirage put on by Loki to distract Thor.
However, inside Hulk's psyche, Bruce Banner connects to the augment Hulk and absorbs every punch he's ever taken by Thor, which allows him to push up enough for Mjolnir to fall through his body.
Unlike Mjølnir, however, the weapon is not enchanted to prevent those deemed "unworthy" from holding it, making anybody with sufficient strength capable of using the weapon.
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.
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.
Loki is confirmed to be worthy of lifting Thor's hammer, Mjolnir, for the first time in official Marvel canon. In The Immortal Thor #5, Loki confidently catches and wields the hammer, showcasing his growth and heroism.
Jarvis doesn't lift Thor's Hammer. Jarvis is an AI. Vision lifts Thor's Hammer. Vision is still very new, freshly created, and hasn't done anything yet that would not make him worthy.
J.A.R.V.I.S. is an artificial intelligence created by Tony Stark, who later controls his Iron Man and Hulkbuster armor for him. In Avengers: Age of Ultron, after being partially destroyed by Ultron, J.A.R.V.I.S. is given physical form as Vision, physically portrayed by Bettany.
Vision wasn't made in 2014, which is when Nat, Clint, Nebula, and Rhodes went. It's the same reason why Heimdall, Loki and Gamora also didn't came back by Hulk's snap! They died in Infinity War but not got snapped out of existence...
Meanwhile, MCU Phase 4 saw Stormbreaker being wielded by Thor, Gorr the God Butcher, Love, and anyone else who was strong enough to actually lift and swing it. This is because of the respective origins of both legendary Asgardian weapons.
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).
It turns out anyone able of holding his hand out can, doesn't it? Only people who are considered worthy are able to wield mjolnir. Cap was deemed worthy in endgame, that is why he was able to hold mjolnir.
Thanos and Hulk have clashed several times in Marvel lore, with Thanos even admitting he was scared to face the Hulk before acquiring the Infinity Stones. While Thanos is usually the victor, it's generally down to him using superior tactics and technology, rather than simply possessing greater physical strength.
After bashing Thor with an entire stone pillar, Juggernaut managed to separate Thor from his hammer – but was unable to lift it as a selfish brute like him was unworthy of its power.
After bonding with the Enigma Force, Venom summoned Mjolnir from Thor's hand as he went to battle Knull for the final time. Venom combined Mjolnir with Silver Surfer's board, creating a powerful battle axe that allowed him to take down hordes of Grendel dragons with minimal effort.
