While it's fun to watch anime characters display supernatural powers, sometimes it's even more exciting to see how characters with ordinary abilities stack up against people who can defy the laws of reality. To do so takes not just physical strength, but also courage and ingenuity. The strongest normal anime characters possess these things in spades.
Among these characters are Sig Curtis from FMA, who is powerful enough to beat up homunculi despite having no ability to use alchemy himself - he gets the job done with the sheer power of his muscles. There's also Arataka Reigen of Mob Psycho 100, who proves that one doesn't have to be psychic when you have charisma and heart.
These characters don't need powers to be awesome - they're already great. Which ones do you like the most?
If loving your wife is a superpower, Sig Curtis has that in spades. But really, the man has no special powers to speak of - he's just ridiculously strong. When he and Alex Armstrong team up to take down Sloth by impaling him with a spike, Sig doesn't use any alchemy to make it happen. He just uses his jacked body.
Sango is a trained demon slayer whose combat skills and encyclopedic knowledge of all things demonic make her a terrifying opponent. Though she's well-matched with her comrades in just about every conflict they encounter, she doesn't use demonic or spiritual powers to get the job done - she mainly relies on the power of her boomerang. Is anybody else getting Sokka vibes?
In the world of Naruto, just about everyone has some kind of chakra-based abilities - and even characters like Rock Lee who are limited in their ability to use chakra still have powers that a real human couldn't hope to emulate.
Mifune is different. He hails from the Land of Iron, where he serves as a general. In the land of iron, people don't use ninjutsu or other abilities like that. They're samurai, and they fight using expert swordsmanship. Using only his sword and his own physical strength, Mifune is able to stand alongside the Kages in the war against Madara.
As the captain of the 8th Special Fire Brigade, Akitaru Ōbi is a calm, confident person who takes care of his team and prioritizes ethics and kindness above all else. While many of the other members of the brigade have varying forms of fire-based abilities, Akitaru has only his training and his physical strength. Despite this, he doesn't hesitate to take on even the most dangerous Infernals.