A 20-year-old man has been jailed for more than four years for an unprovoked assault that left a Sydney man in a coma.

Michael McEwen, 24, spent eight days in a coma and had a section of his skull removed after being bashed and stomped on near a Bondi Beach bus shelter in December 2013.

David Hona, the man who attacked him, has been jailed for at least four years and nine months for recklessly causing grievous bodily harm.

His maximum sentence is six years and nine months.

The New South Wales District Court heard Hona had been drinking and was on bail for other offences at the time of the attack.

Judge Penelope Hock said the assault of Mr McEwen was a despicable and cowardly act. She also described it as "gratuitous".

She said Hona accepted that alcohol was related to the offence he had committed.

The judge said Mr McEwen's head injury was almost fatal and he has had numerous surgeries after the attack.

The court heard he had been fit and healthy before the attack, but he now suffered permanent side effects from the bashing.

The judge noted the offender deliberately crossed the road to attack his victim.

Another man who was with Hona and who started the argument with Mr McEwen but did not throw a punch himself has already been put on a good behaviour bond for affray.

After the assault the McEwen family launched the Wake Up Foundation to raise public awareness about alcohol-fuelled street crime.

The attack was one of several drunken assaults in Sydney, including the one-punch death of teenager Thomas Kelly, which prompted new alcohol laws.

Outside court Mr McEwen's father Robert said the family hope the sentence acted as a deterrent.

"From our point of view it makes no difference if he gets four years or six years. We just hope we don't hear of him again in terms of any trouble," he said.

Mr McEwen said his son Michael was defenceless and on the ground when he was stomped on.

"It was completely unnecessary," he said.

"The sentence was appropriate."

He said alcohol was behind a lot of the anger in the city.

"In this city there is a lot of anger, with young people there's a lot of anger and sometimes alcohol fuels that anger," he said.

"Successful societies are moderate societies. They don't write themselves off week after week and night after night."