'Vile', 'Un-Australian': 20-Year-Old Charged After Alleged One-Punch Attack Leaves Man Critical

A 20-year-old from Sydney's northern beaches has been labeled "vile" by the NSW government after he allegedly assaulted a man in Sydney's CBD on Saturday night.

Harrison Hronopoulos, from Beacons Hill, was released on strict bail conditions after being charged with reckless grievous bodily harm after the alleged assault at St Andrews Square.

A 22-year-old man was taken to St Vincent's Hospital in a critical but stable condition with injuries to his head and brain, and dental injuries after he was found unresponsive just after 8.30pm.

Hronopoulos faced Parramatta Bail Court on Sunday and was released on strict conditions -- that he report to police seven days a week, not contact any witnesses and not consume alcohol or drugs.

"To have this sort of offence committed at a weekend when we should be celebrating the achievements of our nation, is just vile," NSW Police Minister David Elliott said.

"I believe what's occurred over the last 24 hours is un-Australian."

"I believe that what we expect from the community is much higher standards and I share the police force's concerns that the events of yesterday in the city is just a culture that we really need to divest ourselves of."

Harrison Hronopoulos was given strict bail conditions after the alleged attack in Sydney's CBD. Image: social media

Acting Assistant Commissioner of NSW Police Anthony Cooke said alcohol may have been a factor.

"The alcohol may have been a factor but said the alleged incident occurred early in the evening," Cooke told reporters.

"This was 8:30 at night... Early in the evening when you think people should be out and about having a good time."

"It's not good enough. This is about stupidity, people need to take responsibility for themselves."

"People need to be able to go out and have a good evening... where that doesn't happen, you'll end up in the dock."

The alleged 'one-punch' attack occurred in just the second weekend following the repeal of Sydney's controversial lockout laws which were first introduced in 2014 following a string of highly publicised one-punch deaths.

Hronopoulos will appear again at Downing Centre Local Court on February 11.

With AAP.