As Tsunade suggests in Episode 322, “The name itself is power.” Madara Uchiha is first mentioned by the Nine-Tailed Fox in Chapter 308. It’s not up to Chapter 560 — over 200 chapters later — fans finally got to see the character in action. He was so hyped for being such a powerful being that when it came time to introduce him, we weren’t disappointed.
In chapter 560, during the Fourth Great Ninja War, Madara enters the battlefield as an undead resuscitator and single-handedly almost wipes out an entire division of the allied shinobi force, killing hundreds of ninja by summoning two meteorites to level the battlefield. And when he faces the strongest warriors of the Five Great Nations, he plays with them until he releases his true power, leaving them to die.
In addition to being a Sharingan master, he also unlocks both its evolution, the Mangekyō Sharingan, and its more powerful evolution, the Eternal Mangekyō Sharingan. This gives him the ability to use the Ultimate Susanoo, a titanic avatar that Madara states in Episode 339 can “destroy everything in this universe”.
At the height of the war, Madara absorbs all nine tailed beasts and becomes the Ten-Tails’ jinchūriki, something only two others have achieved, one of which was the Sage of the Six Paths. Even Naruto and Sasuke, enhanced by the Sage of the Six Paths himself, cannot stop him when he is the strongest in the series.