Shiro eventually declares him as the last Rider. All the other Riders had died, but it was Shinji's death in Episode 49 that devastated him, as he had finally accepted Shinji as his best friend. Shinji's dying words urged Ren into bringing the war to an end. Shiro Kanzaki brought him to fight the remaining Rider, Odin. As Ren was about to lose, Shiro Kanzaki was tormented by his sister Yui Kanzaki's words, and self-destroyed Odin, thus making Ren the final Rider. The wish appeared, and Ren used it to save Eri's life as he had originally intended. Returning to the hospital where Eri laid, she wakes up to see Ren's engagement ring on her finger, and a loyal Ren, apparently sleeping on the floor. Unbeknownst to her at the time, the battle with Odin had proved too much, and though it is not clearly stated, it's suggested that he died. After Shiro restored time to its proper course after Yui's death, Ren and Shinji gained a new life with no memory of being Riders.
In the movie: Episode Final, Ren, together with the remaining fighters fought one another. He too, like Miho/Femme had mistook Shinji as Ryuga from a battle he witnessed, Ryuga and Femme were fighting with each other. In his case, he thought that Shinji had realized the meaning of the Rider War and demanded they battle. Until he saw the real Shinji getting absorbed into Ryuga he understood and battled Ryuga as well. He confesses his friendship to Shinji after witnesses Shinji finishing Ryuga off an Yui dying. In the 13 Riders TV Special, Ren sees Shinji taking over the Ryuki deck after its last owner dies, and demands the deck be returned. He warns Shinji, but later after setting Shinji up as plotted with the other Riders (in a form of a truce between the Riders) he couldn't bring himself to finish Shinji off, which their friendship developing. In the end, he pushed Ryuki out of the way and took Verde's Final Vent. He shook the damage long enough to kill Verde with his Final Vent and shortly afterwards, he died oi Shinji's arms after giving him the Knight deck.
Knight's Final Vent is Hishouzan, running at the opponent with Wing Lancer in hand as Darkwing lands on its master's back to form a cape as he leaps into the air, wrapping himself with the cloak as they descend in the form of a drill using Wing Lancer as the tip to impale the opponent. Kamen Rider Knight Survive is assumed by using the power of Survive Shippu Card given to him by Tezuka before his death. In this form, Knight's Rider Visor transforms into an arm-mounted scabbard called Dark Visor-Zwei, which could transform into either Dark Arrow or the Dark Shield. His Final Vent is Shippudan, riding Darkraider as it turns into a missile to run through their opponent.