The group earlier fought with Ricky Rowlands outside the Ibis Hotel in King Street, which was housing homeless Victorians during COVID-19 lockdowns.
Mr Rowlands' ex-partner Candice Harper, her new boyfriend Jamie Holt and his acquaintance Benjamin McCartin returned to their room, which was monitored by security guards, as Mr Rowlands stayed outside the hotel.
But there was "no legal or moral" reason for the trio to later leave the hotel room, armed with a knife, other than that they intended to kill him, prosecutor David Glynn told the Supreme Court on Tuesday.
Mr Rowlands, 46, died in hospital the day after he was stabbed during the October 2020 brawl.
Harper, Holt and McCartin, faced a pre-sentence hearing after being found guilty of Rowlands' murder by a jury in December 2022.
Mr Rowlands' family remembered him in statements read to court as a loving father with a "cheeky grin".
"The crime of murder is so heinous," his sister Tracey Rowlands said.
"There are simply no words to describe the heartache and pain I feel every day to understand the choices you have made to commit this crime."
Mr Rowlands and Harper's daughter, who is still a teenager, said she lost both her parents that day.
"I don't want to believe my dad is dead and my mum is also gone, in more ways than one," she said.
"I did hate everyone for what they did to my dad, I wanted revenge and for them to hurt, but I don't hate anyone anymore - hatred and revenge isn't going to bring him back."
Mr Rowlands visited the hotel on the evening of October 10 and a brawl ensured, with McCartin and Mr Rowlands wrestling under a car before the fight was broken up.
McCartin, Holt and Harper went back to their room and returned 90 minutes later, about 9.30pm. A knife was handed to Holt and then passed onto McCartin, as another fight spilled into traffic on King Street.
Mr Rowlands was knocked to the ground with a glass bottle and then stabbed three times by McCartin.
Harper and Holt helped to hold Mr Rowlands to the ground while he was stabbed, Mr Glynn said.
As Mr Rowlands lay bleeding to death in a gutter, Harper stood over him and hurled abuse.
Mr Glynn said the group decided they would kill Mr Rowlands when they returned to their room after the first fight.
"This murder arises in the context of a three-on-one assault using knife, which is a deadly weapon, in a public place," the prosecutor said.
Harper's barrister Alexander Patton said his client's PTSD stemming from childhood trauma was triggered when Mr Rowlands flung her onto the road during the second fight.
He said this triggered the stabbing.
Mr Patton said Harper did not leave the hotel room with the intention to kill her former partner, she left because she was looking for their daughter.
The trio were taken back into custody and will be sentenced at a later date.
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