Full Spoilers Below

In AOT, there is a race called the eldians who can transform into a titan(giant) due to a power inherited by their progenitor Ymir Fritz. Over the millennia, they conquer and subjugate the entire planet and rule as a master race. One of their kings however, Carl Fritz, is overcome with guilt with how they have treated the conquered races and decides to destroy his empire and his people.

He orchestrates a civil war and with a collaborator family ensures that the Eldian empire collapses and 7 out of the 9 titans fall into the hands of a formerly subjugated nation named Marley. He takes a few of his people and noblemen and flee to the Island of Paradis.

The Eldians of the Island are memory wiped by the King to believe that they are the last humans on earth and there are only titans out there.

Meanwhile, Eldians in the former empire are forced into ghettoes and turned into an oppressed slave race, forced by their former servants to be soldiers and laborers. They are seen as the race of devils who must atone for their ancestor's sins. Every Eldian child there is brainwashed from birth to hate his people and see their destruction as a laudible goal.

The founding titan remains on paradis and Marley sends brainwashed eldians to reclaim it. These brainwashed eldians despise their own race and fight against them for the benefit of their oppressor.

Eventually Eldians on Paradise regain the founding titan from their traitor kings and deposes them. They regain their history but find out that they have fallen behind the rest of the world in technology. They are stuck essentially in the napoleonic age whereas the rest of the planet has moved onto WW1-era technology.

The Eldians of Paradis Island look for peace with the rest of the world, they have no desire to reclaim their empire or even liberate their brethren in the continent. They simply want to be left alone in peace.

But the rest of the world would not allow it. They are the devil race that once conquered the world, they cannot be given another chance. The whole planet mobilizes their militaries for a final invasion and genocide of Paradise island.

In desperation, a group of radical nationalists seize power in Paradis and use the founding titan. The founding titan has god-like powers and can release millions of giants onto the world to crush humanity to dust. A civil war ensues and the protagonist of the story, Eren Yeager, seizes the power and unleashes this ''Samson option''.

In a choice between sitting down and letting the world kill his people, and striking back and genociding the world first, he chooses the latter.

The story doesn't shy away with an easy solution. He unleashes mass genocide against the world to save his people.

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As you can see, the story contains themes like white guilt, a traitor elite, a world that hates you and will not let you live in peace and a zero-sum game of genocide or be genocided.