Rimuru

Once she evolved into a kijin and gained a name, Shion became Rimuru's enthusiastic bodyguard and self-appointed secretary, and she often competed with Shuna for Rimuru's attention.

While Rimuru would ordinarily have little trouble in a one-on-one fight, Milim was even more powerful than Rimuru could handle.

Being that he was just recently transformed into a Demon Lord, Rimuru was initially perceived to be weaker than Clayman, who was undoubtedly more experienced.

Diablo defeated Violet with ease in their duel, and Rimuru didn't even break a sweat defeating Lacua in a midair battle over Raja's castle.

In the course of their fight, Rimuru even had his arm cut off by Benimaru, though his healing abilities allowed him to regenerate without an issue.

It was bad enough that Rimuru made eating her food into a punishment for his people, as seen with Gabiru earlier on.

Milim hoped to use her full strength, but Rimuru asked her to hold back somewhat.

Now she's one of Rimuru's best allies as well.

Rimuru could easily survive any Grand Line island and convince other like-minded warriors to join him to form a new crew, perhaps called the Slime Pirates.

Shion is a cheerful deredere ogre who is evidently even more loyal to Rimuru than to her own tribe's prince, Benimaru.

That Time I Was Reincarnated as a Slime, Rimuru Tempest, is endowed with several powerful skills.

In the series, 37-year-old corporate worker Mikami Satoru is fatally stabbed and reborn in another world as a slime named Rimuru Tempest.

Upon her summoning, Beretta evolved into an Arch Doll, granting even more powers as she became Rimuru's guardian entity.

Considering what Rimuru is capable of, it's fair to say that if Milim can easily challenge him, she is definitely a tier or two above Kagura Mikazuchi.

Rimuru Tempest may just be the cutest slime that ever lived.

That Time I Got Reincarnated as a Slime presents an enjoyable contrast between the simple slime protagonist and the absurdly powerful, dynamic being Rimuru Tempest actually is.

Their human and slime form is adorable and recognizable, and, unlike most anime protagonists, Rimuru doesn't want to be the best, but, rather, be good enough to protect their people.

When using this ability, Rimuru is often facing an opponent, such as with the Orc Lord, Charybdis, and the Sky Dragon.