Dalek 3 (The Only Good Dalek)

This Dalek was a Dalek Strategist captured by the Space Security Service during the 41st century in a war against humanity and the New Dalek Paradigm and placed on Station 7. It was later one of 10 captive Daleks, itself numbered 3, apparently reconditioned to defend the station against a Dalek force that invaded the station in search of "the Abomination" where it was rendered inactive.

After the battle, it was found by Amy Pond and Space Major Jay Bourne and pretended to be under their control as it went in search of the Abomination. Professor Weston planned to use the Dalek's shell to carry the Abomination, actually a tamed Dalek, but a Dalek agent switched the tanks around and the aggressive Dalek mutant was put back in its own case and prepared to attack the humans when they weren't prepared. It was destroyed by a Dalek Drone for failing to ensure the base's safety. (COMIC: The Only Good Dalek)

Behind the scenes
Dalek 3 is not actually referred to as such in The Only Good Dalek. However, during the process of "converting" the station's captive Daleks, Jay orders them all numbered and designates a Dalek Scientist as Dalek 1. It can be safely assumed that this pattern was continued with the other nine Daleks.