Ongoing by snakeboy33. Infinity has been described as the opposite of Zero.
Infinity first appeared during the wedding of Cornelia li Britannia, and Gilbert G.P. Guilford. After making a promise to kill everyone in Ohgi and Villeta's wedding picture, Infinity outmaneuvered Zero, and stabbed him through the chest, but not fatally. He would then escape, using his Knightmare, the Nidhoggr.
Infinity would later start his villainous rampage, by attempting to kill Kallen. And while the technologically superior Nidhoggr managed to trump the Guren, Lelouch (not Infinity) could not bare to actually kill Kallen. Infinity would later get Kallen on his side, and Kallen would become Infinity's right hand woman, becoming known as Crimson. Seeing the use in Jeremiah, Infinity then declared his intention to kill him. While he effortlessly defeated all of Jeremiah's escorts, and Jeremiah himself (with Crimson's assistance), Infinity would not actually kill Jeremiah, instead revealing his true identity, and having Jeremiah swear loyalty.
Infinity would be challenged by Xingke later, and the two would square off against each other. While Xingke nearly defeated Infinity, with the Shen Hu modified into the Shen Hu Feng, Infinity would ultimately triumph. The battle resulted in the Shen Hu Feng's destruction, and Li Xingke's death. After his death, Infinity would challenge Gino and Anya to a battle, where while Infinity's Knightmare was disabled, the combined forces of Jeremiah and Crimson managed to defeat both Knights of the Round.
Infinity vs. ZeroEdit
Infinity would later be challenged by Zero himself to a one on one battle. The two did ultimately fight, in which Zero's St. George got the better of Infinity's Nidhoggr. However, Infinity survived, and managed to crush the St. George before the Nidhoggr exploded. Lasting through the blast, Infinity and Zero would have a brief sword battle, before Infinity got them shot up to the roof accidentally. The two would have a brief spar, which Zero technically won, but Infinity would survive again. Infinity would finally be exposed, as would Zero, and this would allow S.S.'s plans to commence.
After S.S. was defeated, both Suzaku and Lelouch concluded the battle between Zero and Infinity was never to end, and for that reason, the two both became their alter egos permanently, and began a constant war, that kept the world united under the hatred for that single foe: Infinity.