The victim of the current offending said Goundar raped him or forced him to perform oral sex nearly every night from mid October 2017 to early January 2018.
He made death threats to dissuade the victim from moving to a different cell, and on one occasion pulled a shank on him.
The abuse only stopped when an anonymous call was made to Crimestoppers, and Goundar was moved out of the unit.
In his victim impact statement, the victim said he had let Goundar run his life for too long.
He could no longer trust people, and because he could not double bunk with people in prison anymore he was becoming isolated from others.
"I feel everywhere I turn I see you and I will never be able to get away from you," he wrote.
"Today I still fear retaliation and revictimisation for coming forward and for taking this all the way to court."
Justice Karen Clark said aggravating features of Goundar's offending included the victim's vulnerability, Goundar's predatory behaviour, his intimidation and violence, the scale of the offending, and the "degrading and cruel element" to it.
"You not only sexually violated [the victim], you humiliated and debased him," she said.
When interviewed for a pre-sentence report, Goundar refused to answer questions relating to the offending, and was assessed as having a low prospects of rehabilitation.
Another report said Goundar was "sadistic and domineering".
Prison file notes also showed a pattern of making sexualised comments towards female prison staff, and aggressive physical advances towards male staff.
Justice Clark had to choose between imposing a 17-year jail term with no parole, or preventive detention - an indefinite sentence which allows an offender to be kept in prison for as long as they are considered a risk to society.
She chose to impose a preventive detention sentence with a minimum non-parole period of 10 years.
Justice Clark also noted Goundar would be deported to Fiji if he is ever released from prison.
The Hamilton offending
In the earlier offending, which happened in 2011, Goundar and his co-offender, Ashumendra Prasad, spotted two teenage girls - 15- and 17-year-old cousins - walking along the side of the road.
They lured the girls into a car with the offer of food and a ride home, but instead took them to a rural area.
The men got out of the car to urinate, at which point the girls tried to escape. Goundar managed to get a hold of the younger girl, and Prasad punched the other girl in the face as she tried to break Goundar's hold on her cousin.
The older girl fled to seek help, and the men got back in the car and drove the younger girl away to another secluded area.
Goundar demanded oral sex and hit the girl around the head area, screaming at her that she had no option but to comply.
She was raped repeatedly and forced to perform oral sex over the next few hours, until eventually the men let her go.
The horrifying ordeal lasted about four hours.
After a trial in 2013, Goundar was found guilty and sentenced to 16 years in prison with a minimum non-parole period of six years and six months.
Where to get help:
• If it's an emergency and you feel that you or someone else is at risk, call 111.
• If you've ever experienced sexual assault or abuse and need to talk to someone call the confidential crisis helpline Safe to Talk on: 0800 044 334 or text 4334. (available 24/7)
• Male Survivors Aotearoa offers a range of confidential support at centres across New Zealand - find your closest one here.
• Mosaic - Tiaki Tangata: 0800 94 22 94 (available 11am - 8pm)
• If you have been abused, remember it's not your fault.
• Wellington HELP has a 24/7 helpline for people who need to speak to someone immediately. You can call 04 801 6655 and push 0 at the menu.
