Infinite Sign-In, Starting with Naruto

Li Changkong, who has read Marxist philosophy, transmigrates into Naruto. He keeps a low profile and checks in, ready to offer beautiful truths wherever he goes, and steps in to help people save face whenever he can't hold back.

During the Third Shinobi World War, he carpet-bombs the battlefield with ninjutsu and makes a spectacular name for himself. From then on, he crushes the Hidden Mist, controls the Nine-Tails, toys with Danzo, and drives off Madara. He leads the new generation to defeat Kaguya Otsutsuki and usher in an era of peace for the ninja world.

When the Buster Call comes, he turns the tide in a world-shaking moment. He tears through the Holy Land, saves Zephyr, takes down the Four Emperors, and destroys the Celestial Dragons. He points Sabo in the right direction and brings the Great Pirate Era to a definitive end.

Super God Academy... (Multiple heroines. If that's not your thing, please move along.)