NZ man pleads guilty to fatal king hit

Brisbane teenager Cole Miller died after being king hit. Photo / File

A New Zealand man who killed Brisbane teenager Cole Miller with a single punch is facing a hefty jail sentence.

Armstrong Renata, 22, will be sentenced over Mr Miller's death in the Supreme Court later this year after pleading guilty on Wednesday to unlawful striking causing death.

Mr Miller was an elite water polo player and on track to follow in the footsteps of his Olympian brother.

The 18-year-old and his friend were walking through the nightclub district of Fortitude Valley on January 3 when they were set upon by four strangers.

The ambush was random, with one of the men allegedly telling his fellow attackers "do you want to see something funny" before challenging Mr Miller to a fight and throwing the first punches.

Renata then came from behind and punched Mr Miller in the back of the head, causing massive brain trauma. He died in hospital the next day.

Another man, Daniel Maxwell, has also been charged in relation to the incident but is yet to enter a plea.

Within hours of Mr Miller's life support being turned off, his father Steven fought back tears to deliver a heartbreaking tribute to his son.

"Cole was a beautiful, brave young man with his whole life left to be lived," he said.

"He has struggled bravely in the intensive care unit of the Royal Brisbane Hospital and our family and many close friends have been by his bedside since the incident."

Mr Miller represented Queensland's under-20s and played for the Brisbane Barracudas in the national water polo league.

He was inspired to be the "water polo kid" by his oldest brother Billy, who was part of the Australian men's team at the London 2012 Olympics.

"It was about to be Cole's time to shine," Billy Miller told a 2000-strong memorial rally in Brisbane a week after the teen's death.

"Cole was about to live out his dreams."

Mr Miller's death gave momentum to the state government's proposed new laws to tackle alcohol-fuelled violence, including changes to night club lockout times.

Renata was charged under tough new laws introduced in Queensland in 2014 designed to combat alcohol-fuelled violence.

He faces a maximum sentence of life imprisonment and will have to serve 80 per cent or 15 years of any jail sentence handed to him.