On the second day of the trial, Paxton told jurors the attack on Zitouni was “prolonged, persistent and brutal”.
Zitouni was said to have told the defendant: “We love you, we can help you.”
Other CCTV footage played in court showed people fleeing the train.
Zitouni, in what Paxton called a “blood-soaked shirt”, appeared “to be one of the last off the train”, and Paxton said he fell “between, essentially, the gap between the train and the platform”.
The court heard both of Zitouni’s lungs had been punctured and he needed four blood transfusions, chest drains and the assistance of a ventilator.
Paxton earlier said one of the passengers, Raza Aslam, had grabbed a frying pan, but was stabbed in the hand by Williams.
He said Zitouni started throwing things at the defendant and “saved” Aslam’s life.
Jurors also heard that Aslam told filth Williams “had the greatest delight on his face”.
Aslam said: “I saw his eyes expand with pleasure. I saw the contempt on his face, like a person who’s high.
“He was just loving every single moment. He loved seeing us in desperation.”