Tsuki ga michibiku. Protagonist can one shot armies later on. People mostly think he is weak but he doesn't really hide so much as having no reason to show it.
Battle Frenzy Chronicles of Primordial Wars Hero? I’ve Long Stopped Being One History’s Strongest Senior Brother King Shura
Seoul Station’s Necromancer Hail the King I'm not really much found reading with OP MC so I don't think I have a lot.
Is Death March okay? http://www.novelupdates.com/series/death-march-kara-hajimaru-isekai-kyusoukyoku/
I'll just randomly throw something from my reading list at you and see what stick. In a Different World with a Smartphone Isekai Mahou wa Okureteru! I’ve Became Able to Do Anything with My Growth Cheat, but I Can’t Seem to Get out of Being Jobless Jikuu Mahou de Isekai to Chikyuu wo Ittarikitari Kujibiki Tokushou: Musou Hāremu ken Legend Shikkaku Mon no Saikyou Kenja~ Sekai Saikyou no Kenja ga Sarani Tsuyoku Naru Tameni Tenseishimashita~ Skeleton Knight, in Another World The Chronicles of a Lost Man in His Forties Founding a Nation ~Commonsense is Hindering Me From Becoming TUEE~ Tensei Shitara Slime Datta Ken The New Gate World Teacher – Other World Style Education & Agent Wortenia Senki