That Time I Got Reincarnated as a Slime features a truly powerful isekai hero, Rimuru Tempest the slime. He is absolutely loaded with magical spells and abilities, but fans shouldn't take his allies and friends lightly, either. Rimuru has befriended a squad of mighty ogres who've evolved into kijin, and one of them is Benimaru the swordsman.
Benimaru is a master of the blade, and he can also use fire magic and resist enemy flame attacks at the same time. He's always looking for another challenge, and this powerhouse ogre is ready to take on the ninja of the Naruto universe, one at a time. He can defeat many of them in a contest of strength, but a few shinobi are too strong or tricky even for him.
10 BENIMARU CAN DEFEAT: Zabuza Isn't Ready For Benimaru's Flames
Eventually, Naruto power levels left behind early characters such as Zabuza Momochi the assassin, and it shows. Zabuza's main technique is to envelop the battlefield in a thick mist, then slash his enemy apart in a sword-based ambush attack. That won't cut it against Benimaru, who's used to enemy trickery.
Once the fog sets in, Benimaru can use his dark fire magic to blast the mist away with hot air, and he might even catch Zabuza in the flames, too. Even if he doesn't, he can take on Zabuza in a contest of swords and overpower him.
9 BENIMARU CAN'T DEFEAT: Kakashi Hatake Is Too Clever For Benimaru
At the bare minimum, Kakashi Hatake the jonin could hold off all of Benimaru's attacks and find a route to retreat if he isn't in the mood to fight. If he takes the fight completely seriously, though, Kakashi can turn this around and win.
Kakashi is quick and clever enough to study and see through Benimaru's moves, and he could land a deadly Lightning Blade attack on his ogre opponent, then hit him with the Kamui to finish things. Benimaru has no defense against that.
8 BENIMARU CAN DEFEAT: Karui Won't Win A Contest Of Blades
Not all ninja rely on swords or weapons, but some do, including Karui of the Cloud Village. She was the highly capable chunin who was once sent to find a lead on Sasuke Uchiha, and she and Naruto were at odds at first. She and Omoi took on Naruto's squad in a brief fight and survived.
Karui won't survive long against Benimaru, though, who has superhuman strength and impeccable technique, not to mention those fire spells. Karui can use substitution jutsu to extend the fight a bit, but she'll lose sooner or later.
7 BENIMARU CAN'T DEFEAT: Sasori Has Too Many Weapons For Benimaru To Handle
With his remarkable speed, swordplay, and flames, Benimaru could deal a lot of damage to Sasori's puppet collection, but he can't quite finish the job. Most of Sasori's puppets will be mere meat shields to buy Sasori time to use his best weapons and finish off this isekai ogre.
Sasori will sacrifice any number of puppets to set up his two best moves against Benimaru: poison gas, and the Third Kazekage puppet's iron sand jutsu. Benimaru has no defense against that poison gas, and the iron sand jutsu can block Benimaru's techniques. Then, the iron sand can finish Benimaru off.
6 BENIMARU CAN DEFEAT: Yamato's Wood Jutsu Will Get Roasted
Yamato once led Team Kakashi as a smart and capable commander, and interestingly, he can use wood release, just like the legendary First Hokage, Hashirama Senju. With that jutsu, Yamato can trap his foes, cut off their retreat, and far more. He is also highly adept at more conventional shinobi skills.
None of this will help him defeat Benimaru the ogre, especially since wood-based attacks are naturally vulnerable to flames, and Benimaru has some of the hottest fire around. Benimaru is also quick and agile enough to handle Yamato's other techniques.
5 BENIMARU CAN'T DEFEAT: Against Might Guy, Fists Beat Swords
Might Guy is the Leaf Village's top taijutsu expert, and Benimaru will learn the hard way why this ninja is called "Might Guy." Might Guy usually fights bare-handed, but he can also use nunchucks and other ninja weapons to block Benimaru's flame sword.
Once Might Guy opens the gates to access techniques like Daytime Tiger, Benimaru is doomed. Not even he can overwhelm Might Guy in this contest of strength, and he'll be blown away. Still, Might Guy would commend Benimaru's springtime strength.
4 BENIMARU CAN DEFEAT: Hinata Is Too Slow To Handle Benimaru
Hinata Hyuga has come a long way, and she is a master of the Hyuga Clan's unique techniques, including her use of the Byakugan. Those white eyes can detect chakra from afar and see right through genjutsu, though Benimaru doesn't use chakra or genjutsu. So, Hinata needs taijutsu to fight him.
Hinata can give Benimaru a good fight, especially with the Eight Trigrams Vacuum Palm, but that's not enough. Benimaru is still faster than her, and he can use his fire to obscure her vision and take her by surprise. Sooner or later, Benimaru will deal the final blow, and not even the Byakugan can get Hinata out of harm's way.
3 BENIMARU CAN'T DEFEAT: Jiraiya Is Stronger, Faster, & Smarter
Jiraiya is the legendary toad sage, and despite his goofy personality, he is a brilliant and sometimes ruthless shinobi on the battlefield. He is also much tougher than he looks, and not even Benimaru's superhuman strength and techniques could take him down.
In battle, Jiraiya could weave through Benimaru's attack patterns and return fire with a powerful Rasengan to deal heavy damage. Then, he can summon the titanic Gamabunta to finish the job, amphibian style.
2 BENIMARU CAN DEFEAT: Choji Akimichi Is Still Vulnerable To Cutting Attacks
Choji Akimichi used to be the butt of several jokes, but all that changed when he learned self-confidence and realized the full potential of his clan's body-expansion jutsu. He is a massively powerful melee fighter, especially when he has those butterfly wings. He can also roll around as a sphere and blast through the opposition.
Even Benimaru will have a tough time matching full-power Choji in the Shippuden era, but then again, Benimaru has a sword, and Choji's neck is vulnerable. Benimaru can keep Choji busy with flames, then leap high enough to take off Choji's head with a mighty swing of his sword.
1 BENIMARU CAN'T DEFEAT: Mei Terumi Can Melt Benimaru In Battle
The Fifth Mizukage is a talented woman named Mei Terumi, and she has not one, but two kekkei genkai styles to her name, in addition to more conventional jutsu based on elemental releases. She can keep up with Benimaru in battle, and negate his fire attacks with her water-based moves.
Then, Mei can finish the fight with her corrosive kekkei genkai, using either boiling steam or lava to vaporize her ogre opponent. Benimaru might, at most, dodge one such attack before Mei can finish him with another. She won't have any mercy.