It's strange how often Goku gets picked up for fights. This time, we are pitting him against Rimuru Tempest.
Plenty of shonen anime put Goku above pretty much everyone else, even godlike characters that he'd have no real way of defeating. Rimuru Tempest seems to be one of them, despite the power gap being majorly huge.
This article will take a look at their abilities, tactics, and personalities to evaluate who will win between Dragon Ball's Goku and That Time I Got Reincarnated as a Slime's Rimuru Tempest.
Note: This article will contain spoilers for both shows. It reflects the author's views.
Goku vs. Rimuru: A clash of gods
Son Goku
A member of a near extinct race called the Saiyans, Son Goku was sent to Earth to make a better life for himself and he succeeded. He befriended Bulma, beat King Piccolo, and has beaten every challenger since then, though not without help. The Earth-born Saiyan loves to fight, fool around and eat. Son's appetite rivals that of One Piece's Monkey D Luffy, which is saying something. His person vow to defend the Earth and everyone on it shows that he is brave and compassionate.
As for power, Son's first fight with Beerus in Super Saiyain God form shook the universe with every punch that connected. He's been able to use the Spirit bomb to kill Kid Buu, and outlasted everyone even when exhausted to emerge as one of the last standing in the Tournament of Power. He has barely begun tappint into his Ultra Instinct form and his new zen form, but he can overcome most fighters in his universe and also from other universes.
The Sayian's primary weakness, however, is his naivete. Son has been more than willing to give villains a fair shot at beating him, including letting them charge to their full form (Frieza) or giving them a senzu bean (Moro). This has backfired several times, especially against Moro who became so powerful that Vegeta had to come and help Goku beat him. Frieza, on the other hand, tried to shoot him in the back and suceeded in Golden form.
He has also needed aid more often than not to finish the job. For example, he has required Vegeta's Forced Spirit Fission against Moro, Frieza and Android 17 against Jiren, Vegeta and him fusing against Broly, Gohan to beat Cell and a massive spirit bomb to beat Kid Buu.
Rimuru Tempest
After dying from a stab wound inflicted by a passing robber while trying to protect his junior co-worker Tamura, Satoru Mikami was reborn as a slime named Rimuru Tempest in a fantasy world. Blessed with immense healing abilities, he set out to learn a bunch of different skills, make friends, and become king of the monsters along the way. He's perfectly pleasant and kind until he becomes angry. His appetite can rival Goku's since he's a slime and has access to Hammerspace.
As for his powers, according to a variety of sources, the slime/human hybrid has access to a Black Sword that cannot be destroyed, bent, or overloaded, as well as a large variety of magic spells. By the end of the series, he's a god with no real weaknesses or vulnerabilities to speak of. An attack needs to destroy him on a physical and spiritual level to guarantee death.
Tempest can also destroy things on an atomic and spiritual level. He can absorb attacks and use them better than their original users because of his sharp, analytical abilities. He heals quickly and can get back into a fight without wasting time.
Rimuru has pain nullification, spirit nullification, and craft healing potions, and he can nullify physical attacks and alter reality perception. With divine protection, he is too overpowered to have any real weakness.
Goku vs. Rimuru
On comparing the two fights, one has to conclude that Tempest wins easily. Rimuru is like Nintendo's Kirby, he can absorb whatever he eats whether it's weapons, elements or people.
The only question, however, is if Tempest's powers will work elsewhere. He is overpowered in his own universe, but will that be valid in other universes? Of course, Tempest does have the ability to traverse dimensions at will and create barriers of interdimensional space.
There is UI to consider with the speed advantage it gives. Goku is a multi-versal warrior who moves faster than light. Despite going in one direction for most of the series, there's a question of whether Rimuru's powers reach that level of strength. Goku also has a Zen form, and the ability to sense other universes and their dimensional energy.
If the slime can keep the Saiyan from charging up, or avoid Ultra Instinct triggering, Tempest will beat the Saiyan. However, even one small mistake can cost him heavily. It is not as clear cut as "one stomps the other" since Rimuru's healing factor does not change how Goku gets stronger after every fight, especially when beaten near to death. Moreover, the latter still has room to develop his abilities.
They are both good people, so it's not like they'd really fight to the death. Frankly, it'd be much more fun seeing them have an eating contest.