This is one of the most powerful victim impact statements you’ll ever watch.

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As Alivea Goncalves, the sister of Idaho murder victim Kaylee, took the stand to stare down Bryan Kohberger at his sentencing, her voice didn't tremble once. She shed no tears as she stared down her sister's killer.

She stood to deliver her victim impact statement, as the killer of four University of Idaho college students was sentenced to life in prison, following his "guilty" plea deal; a deal which saw him avoid a trial and the possibility of the death penalty.

The "big sister" had to do something no sibling should ever face, but she displayed incredible courage as she took down her sister's killer with her words.

Watch: Alivea Goncalves' victim impact statement. Post continues after video.

Goncalves started her statement by telling Kohberger to "sit up straight when I talk to you."

Throughout her speech she berated and belittled the killer, attacking his sense of importance.

"No one is scared of you today. No one is intimidated by you. No one is impressed by you. No one thinks that you are important. You orchestrated this like you thought you were God. Now look at you, begging a courtroom for scraps," she said.

"You spent months preparing and still all it took was my sister and a sheath. You worked so hard to seem dangerous, but real control doesn't have to prove itself.

"The truth is, the scariest part about you is how painfully average you turned out to be. The truth is, you're as dumb as they come, stupid, clumsy, slow, sloppy, weak, dirty."

The courtroom erupted in applause as Goncalves closed her statement.

Alivea Goncalves. Credit: AP via AAP.

"You want the truth? Here's the one you'll hate the most. If you hadn't attacked them in their sleep, in the middle of the night like a paedophile, Kaylee would have kicked your f—ing ass."

She even used Kohberger's past criminology research against him — making use of the questions he once drafted in a survey to killers — the same questions she now has of him, taunting they may sound "familiar."

Goncalves shared that Madison Mogen, Kaylee's best friend and another victim, was also like a sister to her as she told Kohberger of their kind natures.

"The truth about Kaylee and Maddie is they would have been kind to you. If you had approached them in their everyday lives, they would have given you directions, thanked you for the compliment, or awkwardly giggled to make your own words less uncomfortable for you," she said.

Madison Mogen and Kaylee Goncalves. Image: Supplied.

The 10-minute address was a powerful masterclass in what to say to a "remorseless" killer.

Kaylee's mother and father, Steve and Kristi Goncalves, were also amongst those who delivered victim impact statements, with the angry father turning the podium towards Kohberger so he too could stare him down.

The Goncalves family have previously said they were "beyond furious" with the plea deal as they wanted Kohberger to face the death penalty, and a trial, which may have answered the unresolved questions about the case.

Kohberger was sentenced to four consecutive life terms without the possibility of parole over the murders of Madison Mogen (21), Kaylee Goncalves (21), Xana Kernodle (20) and Ethan Chapin (20).

The four students were killed in the early hours of November 13, 2022 in the sleepy college town of Moscow.

Following Kohberger's sentencing, the Moscow Police Department released around 300 documents related to the investigation, which are shedding new light on the case.

The documents revealed how each was killed, and that in the weeks leading up to the murders there were strange occurrences around the rental home, such as the front door being found wide open.

Goncalves also reported to friends she was concerned she had a stalker.

Feature image: AP via AAP.