Dhieu Manoah, 32, was drinking a beer and had just arrived on the floor of his friend's Collingwood apartment when he was killed by Brendan Wayne Harrison, 34, in March last year.

Harrison, who pleaded guilty to manslaughter, on Monday faced the Victorian Supreme Court, where he was sentenced to a total of nine years and nine months in prison.

Justice Jane Dixon said Harrison had not slept in four days before the "violent and extremely dangerous" attack after heavy consumption of the drug ice.

She said he turned his anger from a dispute with his partner, Amour Maler, onto Mr Manoah, a former refugee and Victoria University civil engineering graduate.

"You were in the throes of a severe addiction to alcohol and drugs," Justice Dixon said.

"You were angry and irrational about Amour's rejection of you and you were brandishing the knife and yelling.

"Your attack on Dhieu was unplanned and spontaneous (and) while violent and extremely dangerous, was not sustained or persistent."

Justice Dixon said Harrison's moral culpability was also somewhat lowered by his "profound childhood deprivation".

This included exposure to family violence, drugs, alcohol and homelessness from an early age.

Harrison, a regular drug user since the age of 14, became angry and aggressive toward Ms Maler after smoking marijuana, the court heard previously.

Ms Maler's friend Liban Omar, who lived in a unit upstairs in the same Hoddle Street building, came to check on her while Harrison was in the shower.

As they spoke on the ground floor, Harrison went to the other man's apartment and demanded to know where Ms Maler and Mr Omar were.

He then punched Mr Manoah in the face as he sat on a bench in Mr Omar's loungeroom.

Mr Manoah briefly left the building.

But he was killed by Harrison after getting out of the lift back on to Mr Omar's floor.

"He decided to stab an innocent stranger who just happened to be in the wrong place at the wrong time," prosecutor Grant Hayward told the court.

Harrison yelled out to Mr Manoah's friends that he was bleeding after leaving a 12.5cm-deep wound that pierced his heart.

"You guys are dogs - you should really check on your friend," the 34-year-old said.

Mr Manoah, who was born in South Sudan, became an Australian citizen in 2011.

"I don't know how my family will get over this," one of his seven siblings said in a statement.

Harrison must serve at least six years and six months behind bars before being eligible for parole.

Australian Associated Press