That Time I got Reincarnated as a Slime, or Slime for short, is one of the most popular isekai anime of all time, boasting an impressive three seasons with another on the way as well as a movie. Like most fantasy anime, it has many different races of monsters, different magical abilities called skills, demon lords, etc. Unlike most other fantasy anime, though, there is an incredible amount of depth to the power system and world-building that no other series is able to replicate.
For some anime watchers, this can actually be a negative since it's hard to keep up with the ever-expanding cast of characters and how strong they are, which is where this list comes in.
10 Carrion
Carrion, the Beast King, is a beast person, former demon lord, and current ruler of the kingdom he created, Eurazania, and his power more than speaks for itself. He held his own against Milim Nava, someone who even other demon lords fear, and forced her to fight all out against him, which did end in his defeat, but it showed he wasn't a slouch when it came to combat.
Although he had the title of a demon lord, he technically wasn't since he hadn't awakened, which is what held him back from being stronger and higher up on the list. It's worth noting that Guy, one of the oldest demon lords, saw potential in Carrion and thought he would evolve to true demon lord status eventually. Shion From Reincarnated As A Slime Looking Excited
9 Shion
Shion the Kijin is a fan favorite, and for a good reason. She is a loyal servant of the series protagonist Rimuru and serves as his secretary and bodyguard, a title she takes very seriously, having defended Rimuru on many occasions. On one such occasion, she fought the unawakened demon lord Clayman and absolutely destroyed him without breaking a sweat.
This means Shion could easily be considered a demon lord in her own right if she didn't want to serve Rimuru, and she is more than a match for anyone who isn't a proper demon lord. Shion also doesn't lack courage, as she gave her life to save a defenseless child from invaders.
8 Diablo
Diablo's newest addition to the protagonist's team is an interesting case as most of his power is implied off-screen, but what he does on screen is just as impressive. Diablo single-handedly defeated an incredibly powerful wizard who he technically should've been weaker against. He also fights a hero, Shizue, to a standstill without trying, and it's later revealed that he could've defeated her easily if he wanted.
Diablo is also heavily implied to be Noir, the father to all black-colored demons, making him one of the oldest and strongest things alive, so the anime has barely scratched the surface of what he's capable of.
7 Benimaru
Another fan favorite, Benimaru the Kijin, is a former ogre prince who now serves the protagonist Rimuru as his Samurai General, a title he absolutely deserves. At his peak, Benimaru was to take down a lesser form of Charybdis, a monster made of pure magic that gave even Rimuru trouble. He did this single-handedly and with one attack. He also defeated hundreds of Orcs at a time during the battle against the Orc Lord when he got revenge for his clan.
Benimaru is the strongest of Rimuru's forces by a large margin, and it's not even close. In another world or alternate reality, Benimaru could've been a demon lord in his own right.
6 Hinata Sakaguchi
Hinata is an interesting case because she's the only human on the list, but make no mistake, she has every right to be here. She is one of the few people who can claim to have almost killed Rimuru, which is no easy task, thanks to her sword, which attacks the spirit of anyone it cuts and always kills with seven hits. It's no wonder she's become the number one monster slayer in the known world.
The sword alone would be enough to make her a threat, but Hinata also boasts some of the strongest holy magic in the world of Slime, which can even kill lesser demon lords. When it comes to peak human performance in the world of slime, Hinata Sakaguchi is at the top alone.
5 Clayman
Demon lord Clayman is a scoundrel who plays with people's hearts, but his power is unquestionable. Clayman's abilities allow him to control nearly anyone giving him the nickname Puppeteer, but this small aspect of his power isn't what puts him on the list. Clayman's claim to fame is that he became a true demon lord like Rimuru, giving him physical abilities far beyond anyone who wasn't on a similar level.
Unfortunately for him, Rimuru was above and beyond his level and destroyed Clayman even in his awaked form. It's worth noting that demon lord Carrion and demon lord Frey renounced their titles as demon lords upon seeing what a true demon lord, Clayman, was capable of.
4 Rimuru Tempest
We finally get to the series protagonist, Rimuru the slime, whose feats are plentiful and incredible. To start out, Rimuru was reincarnated into the world with an ability that allowed him to steal other people's abilities by eating them, called predator, which he uses throughout the series to accrue power. A great example of this is when he defeats and eats the Orc Disaster and obtains the demon lord's seed, which allows him to become a demon lord later on.
On top of his overpowered ability and true demon lord status, Rimuru is able to fight and hold his own against Milim, who is known to be one of if not the physically strongest demon lords. He also does this while not actually trying to hurt Milim in any real way.
3 Milim Nava
For the entire series, Milim Nava the Dragonoid is used as the benchmark for truly strong fighters, and for a good reason. The mere mention of her name is enough to send most monsters running because she's one of the oldest and strongest demon lords alive, and she's known to have a temper that can cause entire cities to be wiped off the map. This fact became all too real for demon lord Carrion when Milim wiped out his capital city.
There's also the fact that a punch from her can kill even demon lords if they aren't careful, which nearly happens to Rimuru in their brawl. If it wasn't for Milim's childish personality and aloof nature, she would be a threat to every country in the world of Slime.
2 Veldora Tempest
The second character audiences meet in the entire series just so happens to be one of the strongest. Veldora Tempest is one of the four true dragons that can never truly be killed, the storm dragon, and he picked up a bit of a reputation for destruction. Before the start of the series, Veldora had to be locked away by an extremely powerful hero because he was wiping out a city in a tantrum, an event that started the story.
Even during the events of the story, it's abundantly clear how strong Veldora is because every country and king either worships him as a protector or fears him above all else. Perhaps Veldora's greatest feat is taking a punch from Milim that would've killed Rimuru, the same Milim that seemed almost undefeatable until that point.
1 Guy Crimson
Guy is another special case because his power and strength are almost entirely implied, but it's clear by the way other characters react that he is the strongest character seen in the series by far. To start off, Guy Crimson is one of the primordial demons, Rouge, and is perhaps the oldest character we've seen on screen. He also possesses powers that no other character does, like creating force fields strong enough to contain Milim and Veldora, as well as creating pocket dimensions to have meetings with other demon lords.
During the entire demon lord banquet, Guy is the one who leads the conversation and gives the orders; everyone falls in line, and no one questions him. His true strength is yet to reveal itself, but the fact that Guy can contain the previous two strongest characters on this list makes him more than qualified for number one.