Jayadrata, the husband of Dushala, who was the sister of Duryodhan. When the Pandavas were in exile Jayadrata abducted their wife Draupadi. The Pandava brothers rescued Draupadi but could not kill Jayadrata because he was married to their cousin. Hence they shaved his head and painted his face black and let him go. Pained by this treatment worse than death, Jayadrata undertook a penance and received a boon. On a day of his choosing he would stand equal to all the Pandava brothers except Arjun.
Jayadrata's Death
Duryodhan decided that Jayadrata would not enter the battlefield the next day but remain in the camp. His entire army would surround the camp and prevent Arjun from reaching it. The next day saw the fiercest fighting of the Mahabharata war. Single-handedly Arjun, with his chariot driven by Krishna, defeated one after another of Duryodhan's generals. But they kept coming back at him. Despite that just before sunset Arjun was within striking distance of Duryodhan's camp.
However Krishna told Arjun that he would never make it to the camp in time. There was now only one way out. Krishna would use his Maya or divine powers to hide the sun from the sky. Arjun should pretend to concede defeat. Jayadrata would not be able to resist witnessing the spectacle of Arjun's death. He would come out of hiding. Arjun should not worry about the sun having set. He should kill Jayadrata there and then.
This plan worked to perfection. No sooner had Jayadrata died, Krishna again worked his Maya and the sun shone brightly. This is how the incident has been described in the original version of the Mahabharata written by Veda Vyasa Some later retellings of the story have a slightly different narration. Seeing the sky go dark Jayadrata comes out to see Arjun die. The sun then starts shining again and it is then that Arjun shoots the fatal arrow. The possible rationalization for this is that not only must promises be kept but they must be seen to be kept.