His abuse continued over the phone even as the woman lay in a hospital bed needing her partially severed ear glued back together, with police at her side as he yelled and swore down the line.

The woman opened the door to 21-year-old Paul Flanagan the morning of July 29 only for him to step inside and instantly punch her in the face. He punched her repeatedly to the head before she fell to the ground, bleeding heavily from a cut above her eye.

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On Wednesday, Port Kembla Local Court heard Flanagan thought the woman had been unfaithful to him. He punched and kicked at her legs and body as she tried to get away and later picked up a knife and threatened to kill her.

The woman's ordeal ended when neighbours began taking an interest in the commotion, at which point Flanagan took her car keys and drove off in a friend's car.

The woman was left with bruising and swelling to the entire right side of her face and a bite wound to her ear.

Police from the region's domestic violence high risk offenders team arrested Flanagan at a Mount Saint Thomas home the next afternoon.

Police later viewed text messages from Flanagan showing he thought his actions were justified, and suggesting he would attack again.

On Wednesday the court heard Flanagan had grown up in a violent home and that his own mother had died as a result of domestic violence when he was 16.

He started smoking marijuana when he was 11 and moved on to heroin when he was 13, his Legal Aid solicitor, Emma Harrison, told the court.

Ms Harrison called on Magistrate Susan McGowan to find special circumstances for reducing Flanagan's sentence, noting his violent upbringing, need for rehabilitation and concerns he was in danger of becoming institutionalised, having been released from prison five weeks before the assault.

"The facts are quite alarming and distressing," Magistrate McGowan said.

"It's important the Mr Flanagan continue with the [domestic violence and anger management] courses he's doing in custody."

Flanagan was ordered to serve two years in custody, with the magistrate finding special circumstances for reducing his non-parole period from 18 months to 16 months, making him eligible for release from November 30, 2021.