Qara Iskander ibn Yusuf ruled the Kara Koyunlu or Black Sheep Turcoman tribe from 1420-1436. His struggles with the Timurid ruler Shah Rukh show that he was a brave leader, but he was not able to continue developing what he inherited from his father Qara Yusuf and his reign saw the decline and attenuation of the Kara Koyunlu.
Read more about Qara Iskander: The Succession Crisis, Timurid Invasions, Qara Iskander Ousted By Jahan Shah