One of the strongest superheroes in the Marvel Universe is Thor, the Asgardian God of Thunder and wielder of the mythical warhammer Mjolnir. Under Donny Cates and Nic Klein's run, the co-founding Avenger has recently ascended to the throne of Asgard, claiming the powers of the All-Father after Odin willingly stepped down. However, Thor ended up taking on a radically different role as the latest Herald of Galactus, a job that comes complete with its own set of impressive powers. In comparison, Goku, the iconic protagonist of Akira Toriyama's enduringly popular Dragon Ball franchise has achieved an upgrade of his own by mastering the Ultra Instinct transformation, in essence gaining the powers of the gods for himself. With the two heroes now both more powerful than ever, who would triumph in a hypothetical, no-holds-barred showdown between the two fan-favorite characters?
Even before being crowned King of Asgard and subsequently being bestowed the Power Cosmic from Galactus, Thor was already one of Earth's Mightiest Heroes. With superhuman strength, endurance, and speed capable of going mano-a-mano against the Hulk, even without his hammer, Thor was easily one of the strongest Avengers. While wielding Mjolnir, a hammer that can only be lifted by those it deemed worthy, Thor could fly at incredible speeds, manipulate the weather, unleash devastating electrical attacks and command the hammer telepathically to attack even from far distances. As the All-Father, Thor possessed the omnipotent Odin Force that granted him impressive telepathic abilities, the power to generate energy blasts without Mjolnir, teleportation and the power to manipulate matter and energy itself.
Goku is a Saiyan warrior sent to Earth from the doomed planet Vegeta where he quickly became one of the world's greatest martial artists. Trained from a young age by a variety of masters, Goku's Saiyan physiology gave him superhuman levels of speed, strength, and endurance further augmented by a lifetime of intense training. Goku can fly, fire powerful energy attacks including his signature Kamehameha Wave, teleport using the Instant Transmission technique, but also significantly boost his combat strength through progressively more powerful transformations. The latest of these is Ultra Instinct, which gives Goku the divine combat intuition and raw energy of a god, moving defensively on a subconscious level while launching his own devastating array of attacks.
Unlike, say, Superman, Thor doesn't possess any discernible physical vulnerabilities, even without his already impressive upgrades as the All-Father and Herald of Galactus. This makes him a considerably more formidable opponent than the DC Universe's Man of Steel, even with his Ultra Instinct form achieved. In hand-to-hand combat, Goku may still hold an edge over the God of Thunder due to the divine transformation. The preternatural increase in Goku's defensive instincts with the transformed state was first seen when Whis tapped into Ultra Instinct to admire the beautiful scenery around him while effortlessly dodging blows from Goku and Vegeta attacking him simultaneously in a sparring match. And while Thor is deadly at a distance, so is Goku. The Saiyan has his own catalog of energy attacks should he decide not to immediately close ranks with his opponent by teleporting with Instant Transmission.
However, while Goku may have an advantage over Thor in his Ultra Instinct state if the God of Thunder was at his traditional power levels, the Asgardian Avenger's new status quo has made him nigh unstoppable. Thor now possesses teleportation abilities of his own and no longer requires the Bifrost Bridge to teleport around the cosmos at a moment's notice. With full access to the Odin Force, Thor can now manipulate matter and energy itself, and is likely able to absorb and redirect any of Goku's energy attacks. And with the Power Cosmic, Thor now has all of the powers of the Silver Surfer added to his own, from the ability to travel through time, create pocket dimensions to seek refuge or trap opponents and create singularities and stars that could crush even a Super Saiyan God with their immense gravity. Connection to the Power Cosmic also gives Thor a sense of cosmic awareness, allowing him precognitive abilities not unlike the defensive boost Goku receives through the Ultra Instinct transformation.
By and large, Thor could match Goku physically even before gaining the full Odin Force and Power Cosmic, with the Super Saiyan likely maintaining only a slight edge. Having ascended as the Asgardian All-Father and receiving an exponential upgrade through the Power Cosmic, a match-up between Thor and Goku wouldn't even come close -- the God of Thunder is the strongest he's ever been in his entire comic book history. While Goku's Ultra Instinct transformation certainly helps close the power gap between the two somewhat, the level of abilities Thor has gained through the Power Cosmic alone makes him more than a god. In this hypothetical bout, the Asgardian would likely emerge victorious.