any manga the mc has hidden his real power or didn't know that he/she was very strong

I recomend

The breaker
claymore
Dendrobates
Gantz
holyland
Koroshiya 1
(i only saw anime:
Mahouka Koukou no Rettousei
Trinity Blood)

And you can try mangas from this list, tag "hiden pover/s"
https://www.mangaupdates.com/series.html?category=Hidden+Power%2Fs&orderby=rating

also tags "weak to strong", "Hiding True Ability", "deceptively weak looking protagonist"