Another victim was knocked to the ground, before being hit with a golf club while on the ground.
At a different date, a taxi driver was punched as he got out of his car, causing him to fall and hit his head on the ground.
Sau and his accomplices stole the car and drove it a short distance, before setting it on fire.
Many of the victims were of Asian origin, with some of the assaults seemingly planned.
The victims were traumatised, with one unable to even give evidence because of the extent of their head injury. Others said they were still fearful after the attacks.
There were numerous incidents while he was being kept in prison, including prisoners requesting protection from Sau, the discovery of a sharpened butter knife in his cell, and an attempt to intimidate a prison nurse.
Once his six year jail sentence was completed Sau was sent to Christmas Island to be deported. However, there were delays as he appealed the decision to revoke his visa.
While at the detention centre an incident was captured on CCTV, which showed a detainee being attacked by a group including Sau.
The person was eventually pulled to the ground, with cameras capturing Sau stomping on the victim's head twice.
The Administrative Appeals Tribunal of Australia has now rejected Sau's appeal, confirming the decision to revoke his visa and declaring the Australian public needs to be protected from him.
"The reports prepared by the police after interviewing the victims of Mr Sau's offending graphically illustrate the callous and violent assault perpetrated on innocent people for no reason other than that they appeared to be easy targets," the decision said.
Sau had made submissions in his defence, that he was changed and "fully rehabilitated" after undergoing programmes to help him manage violent behaviour.
He said he would be pressured to join a gang if sent back to New Zealand, and wouldn't have any family to support him.
But the AATA decision notes that submission was made in a letter dated four days after the violent Christmas Island detention centre assault.
The decision also said Sau would face the same possibility of joining a gang if he remained in Australia.
It said his visa needed to be revoked, as he presented a "serious risk to the Australian community should he be allowed to stay in Australia".
Australia changed its policies in 2014, to begin deporting foreigners who had served prison sentences of more than a year.
Official figures show about 30 per cent of the deportees sent to New Zealand have since committed further offences here.
