Dalek Sec
Dalek Sec is the leader of the cult and the Dalek attack during the Battle of Canary Wharf against the Cybermen. He shows his leadership by communicating to the enemy, namely, Rose Tyler, Cybermen and The Doctor, and commanding the other three Daleks in which they "Obey". Because there were only four Daleks outside the void, Sec fought alongside the other Daleks against the enemy, and kept checking the status of the Genesis Ark. However, as soon as the Ark was 'primed' and Sec escaped the Torchwood tower with the Ark, he commanded the entire army of Daleks from the sky, while keeping a close watch on the Ark. Because he travelled through the void, he and the other Daleks picked up void stuff, which when the Doctor reversed the flow of the radiation, would suck in all the radiation, including the Cult and the Ark, however he escaped the Void by initiating an Emergency Temporal Shift, with the Cybermen, Daleks (excluding the Cult) and the Genesis Ark being sucked into the void.
Along with the rest of the Cult of Skaro, he ended up in New York in 1930 and established a base beneath the Empire State Building. Taking control of the Empire State construction and forcibly converting humans into "pig slaves" to serve as a labor force, the Cult of Skaro also worked on experiments designed to evolve Dalek-kind into a new form. The Cult recruited the power-hungry Mr Diagoras, who seemed to think like a Dalek the most. Sec turned against the concept of Dalek genetic purity, viewing survival as more important and seeing human DNA as holding useful attributes, as the humans thrive as a species whereas the Daleks had become extinct. Using himself and Mr Diagoras as the test for the Final Experiment, he was transformed into the first Hybrid Dalek.
While in his new body, he began to feel humanity for the first time in his existence, being motivated by emotions rather than the traditional Dalek drive to conquer. Motivated by these, Sec asked the Doctor to help him create more hybrids using human bodies, and started to express his feelings that their creator was wrong. He decided to have the new race live on, different from the Daleks, since if they continued to try to be superior, they would eventually die. However, the other Daleks came to reject Sec's theories and eventually betrayed him while Dalek Caan took control and fueled the other human bodies with pure Dalek DNA. When the Daleks tracked the Doctor down, they took Sec with them, putting him in chains and accidentally exterminating him when he saved the Doctor by sacrificing himself. The Doctor showed his respect for Sec by calling him the "cleverest Dalek ever" and the only creature that could have led the Daleks from the darkness. Ironically, Sec's prediction seconds before his death that if the Daleks continued to look for death and destruction it would find them was to prove completely correct to the Cult. Due to his transformation from Dalek to human, Dalek Sec has been the only Dalek to repent the deaths he caused, and the only Dalek who willingly sacrificed himself to save the Doctor.
His character as a Dalek/Human hybrid is not entirely clear, as, although he eventually feels humanity, it is sometimes also implied that he still had plans to cause destruction. An example would be when Dalek Caan becomes 'controller' of the Human Daleks; Sec responds to this act of treachery with "That was to be my position!" When he was a Dalek, the mutant inside Sec had longer tentacles than other previously seen mutants, and was able to engulf a human in a sack-like membrane.
