Looking for any of three of anime, manga, and light novels with : Requirements: Strong or OP protagonist who isn't afraid to show their power, something like Kenja no Mago.
Well, I don't know about the Kenja no Mago part but here are some recommendation where 'Strong or OP protagonist who isn't afraid to show their power': (I will begin with ones that you might know) One Punch Man Drifters Isekai wa Smartphone to Tomo ni Overlord Tensei shitara Slime Datta Ken D.N.Angel Noblesse Heroic Age Gakusen Toshi Asterisk Ichiban Ushiro no Daimaou Isekai no Seikishi Monogatari Kaze no Stigma Hagure Yuusha no Estetica The Legend of the Legendary Heroes Seiken Tsukai no World Break Kuusen Madoushi Kouhosei no Kyoukan Chrome Shelled Regios Kiba anime Taimadou Gakuen 35 Shiken Shoutai Juuou Mujin no Fafnir Closers: Side Blacklambs Asu no yoichi Darker than black Strike the Blood High School DxD
Just to point it out, OP listed that as an example in their post. As for the OP, I have a few recommendations: LV999 Villager Campione! Hagure Yuusha no Kichiku Bigaku Invisible Dragon No Game No Life Ore to Kawazu-san no Isekai Hourouki
I think this doesn't qualify under the OP's criteria. He said who isn't afraid to show their power but Mushoku Tensei's MC is a beta-male who rarely shows his power.
You should read Kingdom (manga), just because it's THE manga to be honored by all manga readers =P also I'm pretty sure there's plenty of badass scenes there with lots of characters (yes, even side characters)