Kerry Kourpanidis, 37, pleaded guilty to a manslaughter charge after he fatally bashed Warren Hordpenko, 44, in July 2020.

He tackled Mr Hordpenko off a bar stool and repeatedly punched him in the head at the Kingston Hotel, to which he had returned after taking his distressed daughter home and putting her to bed.

A heavily intoxicated Mr Hordpenko had, about an hour earlier, touched Kourpanidis' six-year-old girl on the face and made inappropriate comments at the pub.

Those words proved to be some of the last Mr Hordpenko ever uttered, with the subsequent beating Kourpanidis delivered over just 16 seconds causing an artery at the base of his brain to tear.

Justice Michael Elkaim, who described the attack as "vicious", sentenced Kourpanidis in 2021 to seven-and-a-half years in jail.

The ACT Supreme Court judge ordered the Griffith tradesman to serve at least three years and nine months without parole.

Kourpanidis, who has been behind bars since a few days after the incident, wore a suit in the ACT Court of Appeal on Tuesday as he challenged the severity of his sentence.

One of his barristers, Stephen Odgers SC, argued it had been "too heavy" for Justice Elkaim to sentence Kourpanidis on the basis that 10 years was an appropriate starting point before a 25 per cent discount for the guilty plea was applied.

"it is a relatively low-level assault," Mr Odgers said.

"It had terrible, tragic consequences. But in terms of many manslaughters, it is relatively low level."

Another of Kourpanidis' barristers, Margaret Jones SC, added that the 10-year starting point was inappropriate because it had been used for much more serious manslaughters.

Mr Odgers also argued that Justice Elkaim had erred by describing Kourpanidis' actions as "vigilante conduct" and rejecting the suggestion provocation should mitigate the offence.

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He said "vigilante conduct" needed to be planned or premeditated, but there was no evidence that Kourpanidis had arrived back at the pub with a plan to physically attack.

An inference could be drawn that Kourpanidis had simply intended to "tell [Mr Hordpenko] off", he said, only for him to snap and impulsively attack the victim upon arrival.

Mr Odgers added that it did not matter that the attack had not occurred until about an hour after Mr Hordpenko's inappropriate comments.

"An offence may still be a result of provocation ... even if there is a time gap," he said.

ACT Director of Public Prosecutions Shane Drumgold SC countered that any provocation to commit the offence would have manifested itself when the inappropriate comments were made to Kourpanidis' daughter.

He said Kourpanidis' lawyers seemed to have taken it further and "aggregated a series of events" that occurred prior to the attack.

Mr Drumgold told the court that following the inappropriate comments, Kourpanidis' daughter had trouble getting to sleep.

Kourpanidis' partner had also criticised him for failing to stand up to Mr Hordpenko, and tearfully declared she was going to write the 44-year-old a letter and deliver it to him on behalf of all women.

By the time of the attack, Mr Drumgold argued, the killer was acting on a "snowballing group of emotions" that had evolved to the point they were "completely independent of the actions of the victim".

The ACT's top prosecutor also questioned why, given the hour or so Kourpanidis had to reflect between the inappropriate comments and the fatal assault, the 37-year-old had not reacted more rationally.

He suggested that instead of going back to the hotel, Kourpanidis could have stayed at home and calmed down with a cup of tea.

"Same conduct by the victim, completely different result," Mr Drumgold said.

This suggestion prompted a woman in the public gallery to scoff and remark "what a joke" before walking out of the courtroom.

A full bench of the Court of Appeal, comprised of Justice David Mossop, Justice Wendy Abraham and Acting Justice Stephen Walmsley, has reserved its decision.

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