Lachlan Hutchins, 24, was pronounced dead at Portland District Health in the early hours of August 6, 2019. He suffered five stab wounds, some up to 10 centimetres deep and one penetrating his lungs and heart.

Cameron Oakley, 25, of Portland, pleaded guilty in the Supreme Court of Victoria on Tuesday to manslaughter.

The court heard the two men were long-term rivals with two confrontations occurring in the eight weeks before Mr Hutchins' death.

The first was at Portland's Woolworths supermarket where the pair had a brawl and Mr Hutchins landed at least one punch on Oakley, and the second at a planned meeting at a shed in Pile Court where they were both in possession of knives but only took part in a verbal dispute.

There was also a number of hostile text messages and Facebook statuses sent between the two, the court heard.

Then on August 5, Mr Hutchins was in a car with his girlfriend Chelsea Campbell waiting to pick up her father from a bus stop in Portland just before midnight.

Mr Hutchins got out of the car to use a public toilet on Henty Street.

Oakley, who had gone for a drive to clear his head, pulled over to use the same bathroom.

Upon sighting Oakley's car, Mr Hutchins can be seen on CCTV shadow boxing outside the toilet block.

Oakley then comes out, armed with a pocket knife.

The pair can be seen throwing punches at each other before Mr Hutchins is stabbed multiple times to the abdomen and neck.

While Mr Hutchins was rushed to hospital, Oakley went home and used a grinder to chop the knife into about 20 pieces.

He then sent messages to his friends telling them he had stabbed the victim.

"Bro, I've one-upped you with Lachy. I stabbed him," one text message read.

Phone records also revealed Oakley stating he "genuinely wanted (Mr Hutchins') dead".

"I don't feel guilty for him dying at all," he was recorded as saying in the days after the incident.

On Tuesday, the prosecution said the confrontation was not planned and that Oakley, upon walking outside the rest rooms and being struck by the victim, used "excessive self-defence".

In a victim impact statement, Mr Hutchins' six-year-old daughter said she felt a "dark feeling in (her) heart" when she found out her dad was gone.

"My heart kind of ripped," she said.

"Things aren't very happy anymore because I don't have a dad like the other kids".

Mr Hutchins' mother Tania said she would miss her son for the rest of her life.

"My heart is missing a piece and that piece is my son," she said.

Brother Timothy said he lost of part of himself when Mr Hutchins was killed.

"I physically felt numb," he said, stating he didn't know how to deal with his grief and anger and became addicted to drugs and gambling.

Lawyer Jason Gullaci said the offending occurred in the context of a small-town rivalry between two men who willingly participated in "testosterone-fuelled nonsense" in the eight weeks before the victim's death.

He said the two earlier incidents were important in determining his client's state of mind in the lead up to the offending.

"In unequivocal terms, (Oakley) was scared of Mr Hutchins," Mr Gullaci said.

He said Oakley fully acknowledged the serious offence he pleaded guilty to.

"This involved the unnecessary loss of life of this young man," he said.

"It was entirely pointless and a waste."

The court heard Oakley had a lengthy criminal history involving jail sentences for assault-related offences, including a previous incident with a knife.

He has spent 644 days days in custody on remand.

Mr Gullaci said Oakley was a carer for vulnerable prisoners in custody and was working hard to kick his cannabis addiction.

In a letter addressed to Justice Paul Coghlan, Oakley said he wished to express the "deepest regret and sincerest remorse I feel for my actions that led to Mr Hutchins' loss of life".

"Knowing my actions caused a daughter to lose a father, a mother and father to lose a son and a brother to lose a best friend will forever be my biggest and most regretful memory that I will take with me throughout my life," he said.

"I offer no excuses for the lasting sadness I have caused for Mr Hutchins' family."

Both the prosecution and the defence agreed Oakley was facing a lengthy period of imprisonment.

He will be sentenced at a later date.

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