Bismarck Waldstein

Bismarck Waldstein (ビスマルク ヴァルトシュタイン, Bisumaruku Vuarutoshutain) is a man who bears the title of the Knight of One under Charles, formerly known as the strongest amongst the Knights of the Round before getting surpassed by the former Knight of Zero, Suzaku Kururugi.

Character Outline
He wears a white cloak that the Knights of the Round wear. He pilots the Knightmare Frame Galahad, and keeps his left eye bolted shut. Despite his status and combat abilities, he believes that war should be used as a last resort, and also sees strength without restraint as needless violence. He was previously the Knight of Five.

Second Season
During the second battle of Tokyo, Bismarck leads the Britannian forces guarding the shore against Li Xingke's invasion force. Li and Bismarck battle, with Li unable to defeat him. Bismarck compliments Li's skill when he purposefully takes a hit to move into position to rescue the Chinese command vessel. During Schneizel's attempted coup d'état of Emperor Charles, he intervenes to stop Suzaku's assassination attempt on the Emperor. Suzaku's "live" command urges him to flee before they even begin fighting, indicating that Waldstein is extremely dangerous.

Following the death of the Emperor and Lelouch's ascension to the throne, Bismarck leads three of the remaining Knights of the Round and a squadron of Knightmares in an attempt to remove Lelouch from power. After Suzaku decimates all but Bismarck, Bismarck attempts to use his Geass, which allows him to see a few seconds into the future, to even the odds, claiming that the only person he ever used it against was Marianne. Suzaku's "live" command allows him to overcome Bismarck's Geass, and he slices the Galahad in half. Bismarck dies gasping Marianne's name.

Abilities
Bismarck is proficient in combat with a sword, which he demonstrates when defending Emperor Charles from Suzaku's attempted assassination. He is equally competent in Knightmare Frame combat, being able to engage Li Xingke's Shen Hu on equal terms, and emerging unscathed from the battles fought in Japan between the Britannian Empire and the Order Of The Black Knights.

Geass
Bismarck's Geass allows him to see into the future. The Geass Sigil appears in his left eye which is sewn shut to keep him from using it when not necessary. He is seen using his Geass only several times during his fight against Suzaku. He also states that he has only used his Geass once before against Marianne. How he received the Geass is unknown.

Theory (possible, but not proven)
It is unknown how Bismarck's Geass works, however, the connection between the eye and the brain is not perfect. There is a small delay in the picture of about tenth of a second, basically the vision a person is seeing is 0.1 secs old. If Bismarck's Geass overcame this dilemma somehow and gave him "instant" vision then this would explain how he could see "before-images" (opposite of after-images).

Nightmare of Nunnally
He appears as the Knight of One, as a zombie member of the Knights of the Round in Nightmare of Nunnally. He and the other Knights of the Round who are turned into zombies face off in Sutherland Sieg-like machines against the contingent of forces led by Zero, Suzaku, and Euphemia li Britannia, and personally fights Zero. Upon Charles and Marianne's defeat inside Eden Vital, he concedes defeat with their passing as well, and crumbles into dust along with the rest of the Rounds.

Trivia

 * His Geass ability is strikingly similar to the ability of Fuhrer King Bradley, aka the Homunculus Pride on fullmetal alchemist (2003) and Wrath on fullmetal alchemist brotherhood (2009). Like Bismarck, Bradley can see into the future, though instead of his eye being sewn shut when his ability was not in use, Bradley wears an eye patch.
 * Due to all the Norse mythology references that are present in Code Geass, Bismarck's Geass may be a reference to Odin's power to see into the future.