Tristan Mataora Heather pleaded guilty to fatally attacking Mr Duroux on the Gold Coast in December 2015.
Heather had been celebrating his 18th birthday at the Coolangatta Hotel, where he had more than 20 drinks before killing the beloved grandfather in an unprovoked attack.
During sentencing on Thursday, the court heard Heather chatted and drank with family and friends until the pub closed in the early hours of December 4.
They left and, without warning, Heather punched a man in the head. He was then seen shadow boxing a light pole and soon went to intervene in a scuffle between Mr Duroux and another man with whom they had been drinking.
With a right hook of significant force thrown from behind or beside, he knocked Mr Duroux to the ground causing him to smash his head on the road.
Mr Duroux ended up in intensive care and was kept alive on life support for 10 days before succumbing to his injuries.
Heather fled the scene but was later caught.
Under Queensland's one-punch laws introduced in 2014, Heather must serve at least 80 per cent of his six-and-a-half-year sentence. He is expected to be deported to New Zealand once released.
Speaking outside the Brisbane court on Thursday, Mr Duroux's sister, Lavinia, described the sentence as "pathetic".
"The message that the judge is sending is saying that it’s ok to go out and hit somebody when you’re fully tanked on alcohol… what kind of message is that to be out there?" Ms Duroux told reporters.
"Somebody needs to stamp down on it and say it’s enough. Put the heavy sentence, lay down the heavy sentence that’s supposed to come with the legislation."
In a court packed with family and supporters of both Mr Duroux and Heather, Justice James Douglas described the fatal alcohol-fuelled attack as a "tragic case".
Statements from three of Mr Duroux's children were read, with all hoping justice would be served on their father's killer.
His son, Trevor French, described the day he was told to travel to the Gold Coast as soon as possible from his home in Tamworth, about six hours away.
"After losing my mother at a young age life was already difficult for me and my family," he wrote.
"When I thought life couldn't get any tougher I received a phone call no child should receive - your father is in hospital as a result of an act of violence and there is a slim chance he will make it."
Mr French had slim hopes his father would pull through but was left numb when he died.
"Imagine you've gone to bed and you drift straight into a bad dream, you're anxious and frightened and cannot wait to just wake up knowing it will all be over soon," he wrote.
"Well this is life for me, the only thing is I don't wake up and it's never over."
In October, another New Zealander, Armstrong Renata, was sentenced to seven years' jail for the one-punch attack that killed promising water-polo player Cole Miller.