Kallen vs. The White Knight

Kallen's main rival in the series is Suzaku Kururugi, a soldier in the Britannian military who fights against the Black Knights in the hopes of changing Britannia from the inside. Suzaku is one of the best pilots among the Britannian army and he was given a new Knightmare, the Lancelot with the hopes that he can single handedly take the Black Knights down. He and Kallen fight several times during the series and each times find themselves evenly matched. Each having their Knightmare upgraded with the newest and the best technology.

The first time Kallen and Suzaku fight is in the first episode, when Kallen saves Lelouch by challenging Suzaku in her worn down Glasglow. The second time they fight for an exteneded amount of time, Kallen has the Guren Mk-II and is able to stand on equal footing with the Lancelot by using her Raident Wave Surger. Kallen and Suzaku are constantly going head to head, and each time they are unable to gain advantage over the other.

Although Kallen and Suzaku were on different sides, they never truly hated each other, even on Kamejima Island when Kallen was captured they never tried to hurt each other outside of battle. Their relationship changes during the time when Kallen is in the custody of Britannia as a prisioner. Suzaku attempts to make her spill information on the Black Knights, their location, their plans, and whether or not Lelouch is still Zero, by using Refrain on her. Kallen fights back which makes Suzaku stop when he realizes controlling Kallen would be the same as using Geass which would make him the same as Lelouch. Kallen isn't able to forgive him so easily and as a result, beats him up when she has a chance for revenge.

Not long after Kallen reaches freedom, she finds herself on a brand new battlefield where she finds herself fighting alongside Gino and Anya from the Knights of the Rounds and several other members of the Britannian military. During the time in which Suzaku fights under Lelouch, Kallen finally finds a way to overcome him. They fight a long battle, before Gino sacrifices his Knightmare to give Kallen a clean shot through Suzaku's shield. In her final attack she takes down the Lancelot but her Guren loses power soon afterwards.