Upon killing Eren by severing his head from the spine, Mikasa kissed him farewell. Seeing Mikasa's choice, Ymir abandoned her hold over the Founding Titan, ending both the Rumbling and the Power of the Titans.
As confirmed in the manga chapter 137, titled "Titans," Zeke's death did stop the Rumbling once and for all.
In reality, they were transformed humans known as Subjects of Ymir and had existed for nearly 2,000 years. However, after Eren Yeager's death and Ymir's decision to relinquish her power, all the Titans returned to their human forms, thereby rendering the species nonexistent.
“Over the course of four days after first setting foot on the continental mainland, the Rumbling brought about the complete destruction of the northern continent of Marley along with significant devastation in the southern continent and neighboring nations. Approximately 80% of all human life on the planet was ended.”
Thankfully they stopped Eren and ended the reign of Titans for good, but the manga's ending sheds some light on Karl Fritz, the Rumbling, and its true purpose. The Rumbling was never meant to end the world or stop enemies from attacking. In the end, the Rumbling accomplished Karl Fritz's goal of ending the war.
Eren's goal is to eliminate the entire world except for Paradis, but keeping his fellow Paradisans alive is also extremely important to him, especially his close friends.
Inumaki could have told Eren anything with his cursed speech to prevent the Rumbling.
1 Paradis Was Ultimately Bombed & Destroyed By Its Enemies
Although their technology had improved, Paradis was bombed into oblivion all the same. In the end, it is strongly implied that Mikasa and Armin failed to break the cycle of hatred, leading to the complete annihilation of everything they hoped to protect.
According to his estimations, there were around 573,084 Wall Titans in the Rumbling.
Because of her grief over Eren's death, Mikasa rushes ahead of her comrades and quickly expends all of her gas, stranding herself in the middle of Trost. As two Titans close in on her, she contemplates giving up but is motivated to keep fighting by memories of Eren.
Soon after Eren Yeager's death at the hands of Mikasa Ackerman, the Wall Titans vanish as the Power of the Titans has been relinquished by Ymir.
Eren's death and Ymir's liberation by Mikasa also results in every Titan body turning to dust, and those that had been transformed restored back to human form. Knowing his sacrifice, Eren's friends are grateful for being relinquished from the Titan curse at last, but non-Eldians remain suspicious of them.
2 The Rumbling Killed 80% Of The World
After various difficulties, strategic plans, and devastating deaths, Eren Yeager was finally put to a stop mere days after he commenced the Rumbling.
Levi's ending and its meaning
In the final scenes of Attack on Titan, Levi is seen living in Marley. He's wheelchair-bound and escorted around a city by Falco and Gabi. Levi is implied to live out the rest of his life in a strange, foreign country, his friends either dead or an ocean away.
Needless to say, Levi attacks and beheads Zeke with one swift strike. With Levi killing Zeke, Attack on Titan finally settles the score between the two.
Out of the Nine Titans, the Colossal possesses the most destructive power, and this power was on full display in Season 4 when Paradis Island launched a surprise attack on Marley. Armin possessed the power of the Colossal at this point, and he transformed inside the harbor in the middle of Marley's navy.
Founding Titan
Founding Titan is the first and the strongest Titan of all the nine. If the Founding Titan is someone from Royal Bloodline, then it will possess limitless power.
Approximately 80% of all human life on the planet was ended by the time the Rumbling was stopped prematurely by the combined efforts of the Marley's Warrior Unit and defectors from Paradis Island's Survey Corps.
Grisha was confused by these names, and Kruger admitted that he did not know whose memories he was seeing. Afterward, Kruger willingly allowed himself to be eaten by Grisha, successfully transferring the Attack Titan to him.
Eren and the Titans
In the end of the manga, Eren attempts to destroy the world by reviving Ymir and invoking the power of the Founding Titan. However, Mikasa ultimately kills him, which results in Titans and their powers vanishing from the world.
Eldia lost most of its land as well as seven of the Nine Titans to a newly reborn Marley, and many Eldians retreated and confined to its remaining territory of Paradis Island off from the coast of the mainland.
Eren was devastated by Sasha's passing. However, because of what he experienced and what he had to do to save the Eldians, hearing Sasha's final words made sense to him and brought back memories of when they were younger, and it was easier to hate the Titans for the devastation they had caused.
Sasuke's Susanoo can generate a pair of massive swords that can cut through mountains, so he would be able to cut through the Rumbling Titans with ease.
4 Madara Could Defeat Eren's Founding Titan With A Single Jutsu (Attack On Titan) While Eren Yeager's Founding Titan may have been potent enough to destroy most of the world, he's still surprisingly vulnerable to attack.