Okay, I'll give my arguments. At the time I can't post scans or anything, sorry, but I point out the chapters where the events happened. I tried not to go too long with them, sorry if I did it anyway.
1) Muteba shouldn't have class 5 lifting strength. When grappling with Wakatsuki, he said he was completely outmatched and wasn't expecting the man was that strong (Therefore, this means he miscalculated and underestimated Julius's strength as well, who is stronger than Wakatsuki) and he could only free himself using acupuncture.
2) The only time he did real damage to Wakatsuki was with that hit in the neck, which is one of the weakest parts of the body (And we know that the author of this manga sticks to this kind of anatomical things). His other attacks did like zero damage. So this is not about Muteba being too strong, but what happens is that's a vital, so to speak. A weak point. That's Muteba's fighting style, to strike the enemy's weak points.
3) The only time Muteba received a hit he didn't block or dodge was in 191 and 192 (end and beginning of each chapter, it's the same punch) and despite he stepped back to lessen the damage, still he bled from his mouth. In 193, he blocked a punch and broke his arm in the process (the page has written the word "crack") and then Muteba says "If he lands a clean hit, he'll overcome me in an instant" (which means a normal blow was too much for him). After that, Wakatsuki grazes Muteba's nose with his elbow and despite not having been a clean hit, his nose was left incapacitated.
4) And, yes, Muteba survived a blast core, but the same way you'd survive a shot if it hit in the arm. He blocked it, and despite that, his arm was completely crushed and he was sent flying. If it hit the torso it would have been lethal, as the manga itself points out. Do you know who survived a Blast Core? Julius, it hit directly his torso and he could fight afterward and wasn't sent flying like that (but it hurt a lot if it hit a vital, it would have been game over for him). Actually, ff you see the fight, Wakatsuki didn't land any clean hit, but despite that, he made him a lot of damage.
5) Seeing how he underestimated Wakatsuki's strength, and how even a normal punch could mean game over to him, with Julius it would have even worse. So Muteba saying he could defeat Julius easily was just arrogance from his part (although at that point, the man hadn't used the heart jab, a durability negation technique, yet, and he wasn't expecting to use it against Seki, so maybe when he said he could defeat Julius with 0 problems, he was thinking about using this unexpected surprise technique on him).
6) Let's talk about his fight against Sekibayashi. The first attack Seki landed almost left Muteba on the floor, and he said his attacks were heavy, very heavy to the point that Seki was pushing him back (chap. 143). Then he grappled with Sekibayashi and they were even in the physical aspect (although I can't say the same for the skills). After that, Sekibayashi pulled him out a tooth with a head butt (143). Muteba while using boxing footwork made a lot of damage to Seki, even broke his bones. Later Seki made Muteba scream of pain with a hit (144) and in 145 he proceeds to give him a hit combo that made him a lot of damage (broke his nose and made him bleed a lot). And even his last move after the heart jab in 146 made Muteba bleed too, despite Seki could barely move, and then Muteba said immediately Seki was a real match to him and a true warrior.
7) And, now his fight against Meguro. The manga stated in chapter 71, while Muteba was coughing up blood after Meguro's first attack: "For a moment he stopped moving" and, when grappling, he couldn't free himself with his skills and strength. And, we can't forget he was strangling Muteba and made him bleed with a bite. And, yes, of course, he was outmatched by the mercenary, but Meguro was able to make him damage and showed a superior lifting strength. And the only time Muteba received a clean hit from Meguro, at the beginning of the fight, he was knocked out for a moment, as the manga itself stated.
So, what I believe is: Muteba could keep his tiering, but not for downscaling from Wakatsuki (Wakatsuki was incredibly superior to him to the point of being able to finish him with a normal punch) but for scaling above Kiozan's Raging Vigour, as he could break Seki's bones with his attacks, while Kiozan with this technique couldn't. Or maybe just scale to it, not above, as he broke Seki's bones just after various hits, not with one. His Class 5 lifting strength should be downgraded to Peak Human, as he was shown comparable with Seki and below Meguro in this area, and completely outmatched by Wakatsuki. And his durability... I'm not sure. Maybe a downgrade? Seki could make him real damage and Meguro knocked him out for a sec, but I don't know.
What do you think?
Sorry if the post is too long. HAHA I tried to summarize everything the best way I could.
