A Canberra teenager should spend time in jail after a man he floored with a single blow during a night out in Civic suffered life-threatening injuries, a court has heard.

Tyran Pumpa, 19, was among a group walking towards Mooseheads nightclub on London Circuit when he encountered the victim and several friends in the early hours of March 8 last year.

The two groups got into a verbal argument after one of Pumpa's friends commented on a tattoo sported by a man who was with the victim, police alleged in court documents.

The altercation turned violent when one of the men Pumpa was with shoved the victim.

Friends tried to pull the men apart as they scuffled, but the two men followed the victim to a nearby carpark before Pumpa approached him from behind and threw a single punch to the left side of his face.

The blow caused the victim to black out and fall backwards, hitting his head on the ground. Blood immediately began to flow from his mouth, ear and the back of his head, police allege.

The group then fled the scene.

The victim suffered bleeding on the brain, skull fractures and a ruptured left eardrum and spent three days in a hospital neurosurgery unit.

Police used CCTV footage and an identification parade to identify Pumpa.

He was committed to the higher court for sentencing after he pleaded guilty to inflicting grievous bodily harm in the ACT Magistrates Court in November.

The charge carries a maximum penalty of 13 years in jail.

Prosecutor Keegan Lee argued during a sentencing hearing in the ACT Supreme Court on Monday that the harm Pumpa caused the victim was "significant" and there was a need for specific deterrance.

Mr Lee noted Pumpa's early guilty plea and acknowledged that showed a level of acceptance and remorse.

However, he questioned the voracity of Pumpa's remorse and argued it was not significant enough to prompt a change in his behaviour.

Mr Lee said the offender should spend at least a portion of any jail sentence imposed in full-time custody.

The court heard the injuries caused the victim an increased risk of dementia, ongoing pain due to the skull fractures, hearing difficulties and possible psychological conditions.

Defence counsel Richard Davies said there was "no firm indication of ongoing disability" for the victim.

"The court ought to deal with what is known and not what might or might not happen in the future," he said.

Mr Davies said his client had made attempts to avoid Civic at night and to cut down on his alcohol and cannabis consumption.

He said some people were better equipped to express remorse than others.

Pumpa had underlying psychiatric problems and had experienced suicidal thoughts, which could be addressed under a deferred prison sentence, Mr Davies argued.

Justice Hilary Penfold will hand down her sentence on August 22.