Zero Requiem

Zero Requiem (ゼロ・レクイエム, Zero Rekuiemu) is a plan created by Lelouch and carried out with the assistance of Suzaku and possibly C.C. to end all war and to usher an age of peace. The plan involved focusing all of the world's hatred on Lelouch, then have Suzaku disguised as Zero kill him, dissipating the hatred and allowing the world to focus on more important matters than fighting, such as reconstruction and helping others, thus facilitating peace.

After having stopped the plan of his parents on creating a new world, lelouch and suzaku was unexpectedly seen as accomplices- Lelouch announces that he had killed Charles and is now the new emperor of Britannia with Suzaku as his "Knight of Zero" thus creating a confusion among those who had known their past conflicts. Zero then launches his plan on "destroying the world" starting from making the United Federation of Nations and the black knights as his enemy. Later on, the UNF and the black knights joined Schneizel in fighting against Lelouch. Throughout these fights it was made shown that Lelouch was a dictator who is the enemy of the world- thus making Zero Requiem a complete success. It was never told to the viewers however until episode 25.

Having won the battle against Schneizel and the Black Knights, Lelouch arranges the public execution of The Black Knights' leaders and the United Federation of Nations representatives. When Suzaku, disguised as Zero, interrupts and kills Lelouch, the culmination of the Zero Requiem as they had planned. By directing all the hatred of the world onto him, Lelouch's death will serve to facilitate peace. He dies smiling, saying he is the one who both destroys worlds and creates them. Suzaku is left to play the role of Zero. Nunnally can only watch in shock. When Lelouch falls near her, she takes his hand and realizes that he has sacrificed himself on purpose to bring world peace. Lelouch dies in the arms of a crying Nunnally, who then succeeds her brother as Empress of Britannia.

Aside from Lelouch, Suzaku and C.C., several other key characters knew about Zero Requiem, including Jeremiah Gottwald, Lloyd Asplund, Cécile Croomy, Sayoko Shinozaki and Nina Einstein, while others such as Nunnally, Kallen, the core Black Knights members and Cornelia only realized it during and after his execution.

Suzaku becomes Nunnally's protector in the following months, aided by Schneizel, who Lelouch ordered to specifically obey Zero. The aftermath is narrated by Kallen, who ends up forgiving Lelouch as she has realized Lelouch's true intentions were noble and explains how the world is much better off with all the energy being focused on reconstruction.

Trivia

 * The idea of Zero Requiem is similar to the sacrifice of Treize Krushrenada from Gundam Wing to end all wars.
 * The scene between Suzaku stabbing Lelouch parallels Kamui and Fuuma killing each other to bring peace to the world in both TV version and Movie version of X/1999.