Your entire argument is mut considering Nine himself is but an inferior version of Shigaraki, as both were amped and modified by the same person, Doctor Garaki.
So how is it that Deku was able to heavily injure Shigaraki with 100% only on his arm if there is this huge difference between these forms? Why he claimed he used everything he had against Shigaraki?
In real life using back and torso muscles will never make your punches hundreds of times stronger, your arguments are ridiculous because the difference in power between feats is simply too big to justify this train of logic.
All Might to this day is still a top tier compared to Nine and Full Cowl 100% Deku from the movie.
Except they AREN’T the same scenario.
Nine did not get the same enhancements Shigaraki got. That is clearly shown from his reliance on the tubes, his body itself being weaker, his quirk being different, and that he was the last test subject before Shigaraki. At best you could claim that the tubes he injected himself with were his replacement for the enhancements Shigaraki got, but even then, you would have to prove a lot of things done to Nine were the same as what Shigaraki went through.
Deku can heavily hurt Shigaraki with 100% on his arms but not overcome Nines power because of two reasons.
One, Shigaraki isn’t MEANT to be that strong. The Doctor literally says that he didn’t put as much strength enhancers into Shigaraki to not overburden his brain, something we see happen with Nine when his eyes go white and he loses basically all his thinking other than attack. Shigaraki is INTENTIONALLY not as strong as Prime All Might BECAUSE of Nine, not the other way around.
Two, Nine is flat out stronger with his quirks demonstrably. He’s the last test subject, so logically, he would be the baseline for Shigaraki’s final state. And even then, he doesn’t exactly survive for long, it’s a temporary amp that literally kills him in like 4 minutes. He can temporarily become ridiculously strong, but that’s it, he’s dead after that. The rest of the time? Nine would get stomped by 75% Shigaraki.
If he used everything he had against Shigaraki, why did he not use 100% Full Cowl? Unless your argument is that 45% is the same speed and strength as 100%, which is clearly wrong, there is no reason he shouldn’t have used Full Cowl 100% there. It doesn’t even have to be tier 6, that doesn’t matter. It is stronger than 45% so he should’ve used it if he was really going all out, but he didn’t, so something is simply limiting his usage of it.
Yes, in real life, using your back, torso, hips, legs, EVERYTHING into a punch will increase the force a lot. Will it be by hundreds of times? Of course not.
That’s where the literal fiction aspect comes in. We aren’t talking about a body builder, we’re talking about someone who creates whirlpools with finger flicks. Obviously, for Deku, increasing his base body to 100% would make his punches at 100% ridiculously stronger, because he just went from somewhat normal strength to being able to cleave a city in half.
Name anyone who has compared Nine or FC 100% to All Might.