I am looking for a manga like Hakaiou Noritaka! were the mc looks really weak but is/become really strong.

As long as order exists madness cannot be erased

There is a tag for that : Deceptively Weak-Looking Protagonist

And also many similar threads, here are a few :
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Other than that, most shounen titles with kids as protagonists (or who look like kids) that are pitted against adults might fall into that, meaning 90% of battle shounen.

Here are some titles that I recommend that fit what you want though :
Human Weapon - Katsuo : The MC looks the most like your example (same mangaka).
Gun x Clover : MC looks like a frail kid, shy and always bubbling his words, but actually hides his real strength and personality.
Onepunch-Man : As title implies, overpowered protagonist, but most people in-universe think he looks lame and that he's a 3rd rate super hero.
Mob Psycho 100 : Take Akira's Tetsuo, and make him look frail and you get Mob. Don't pass on this title because of the art, good comedy.
Nanatsu no Taizai : Everyone assume the MC is only a little kid at first.
Black Haze : Another MC that hides his strength willingly
Holyland : Among all the guys street fighting in this manga, the protagonist is definitely the weakest looking one.