Code Geass Ending, Explained
Zero Requiem is a plan to make one man the sole owner of the world's hatred, and then kill him. Whether it worked depends on which ending you count as the ending.
Spoilers throughout. This page assumes you have finished the series.
Code Geass ends on a plan that is only legible in the last few minutes, and then spends a decade being re-litigated by a film that changes the answer. Both halves are worth separating.
What Zero Requiem is
Lelouch takes the throne of Britannia and makes himself the worst thing in the world on purpose. He holds every nation hostage, breaks the alliances he built, and puts himself at the centre of a hatred that had previously been spread across nations, histories and grievances that could never be resolved because they had no single owner.
Then he gives that hatred somewhere to die. Suzaku, wearing the mask of Zero, assassinates him in public, in front of the people he has just terrorised and the prisoners he has just paraded. The world watches evil be defeated by its own symbol of resistance.
The trick is that both roles are performances by the only two people who know it. Lelouch does not become a tyrant; he plays one, at the cost of his life and his name. Suzaku does not kill an emperor; he retires as a person and becomes a mask that anyone could be wearing. Neither of them gets to be thanked, which is the design rather than an accident of it.
Why it is built the way it is
Because Lelouch spends the entire series discovering that his methods produce the outcomes he says he hates. He is the person best equipped to see that the world's problem is not a villain but a structure, and the only lever he has ever been good at pulling is making people follow him. Zero Requiem is that lever used once more, aimed at himself.
It is also an admission. A man who has justified enormous harm on the grounds that the ends warrant it finally names a price high enough to settle the account, and the price is him.
Did Lelouch actually die?
In the television series, yes, and the ending does not work if he did not. The famous ambiguity comes from the closing scene: a cart, and a line from C.C. that could be addressed to someone present or to someone remembered. That was enough to keep the question alive for years.
The 2019 film Lelouch of the Re;surrection then answered it. He survived, after a fashion, with his consciousness held elsewhere and nothing much left of the person, and C.C. spends the film restoring him.
Whether that is a gift or a betrayal is the actual argument, and it is not a question of fact. The strongest thing about the television ending is that its protagonist pays in full and does not get to see whether it worked. A sequel that gives him back is generous to the audience and expensive to the ending, and both of those can be true at once.
One thing to know before you go looking
The compilation films that preceded that sequel are not simply the series recut. They are an alternate continuity, with some events and some deaths changed, so treating everything released after R2 as one straight line will produce contradictions that are not really contradictions.
Endings built on a protagonist engineering the world's morality tend to age in interesting ways. Death Note and Attack on Titan both end on versions of the same question.