Two daughters had lost their dad "because of me", he said.
He asked the families - who were in tears during the apology - if they could ever forgive him.
"If there's a chance to make things right, I will take it. It's too late now, but I just want you and your family now to know how much I regret my actions.
"Through this I have learnt my lesson which I will never forget throughout my life."
Mr Waterhouse married his wife Lepona Sitagata Waterhouse when he was 17 and they have two daughters together.
Today, through a victim impact statement read to the court, she said she was not able to forgive Faletolu for taking away "a wonderful dad and loving husband".
She told how her husband worked hard, with long hours.
He often came home after the children were asleep but would always wake them to see them and to talk to them.
His brother Herbert, known as Junior, described Mr Waterhouse as a "peaceful person... a loving brother, amazing father" and highly-respected member of their church congregation.
Their mother had died from cancer in 2012 and now they have lost a brother.
Older brother Perkins, 27, spoke of his "heartbreak", while father Reverend Perkins Waterhouse battled through tears to pay tribute to a son, " a precious gift".
He turned to Faletolu in the dock to tell him: "May god forgive you, and bless you."
After the dance finished, people were gathering outside to leave when a fight broke out between some females.
Mr Waterhouse tried to help a friend when a fight broke out between males but soon stopped.
The females started fighting again, and it was then that Faletolu assaulted Mr Waterhouse, who fell heavily to the footpath.
Faletolu was chased and detained by friends of Mr Waterhouse, who was unconscious, with a serious head injury involving bleeding on the brain.
Crown prosecutor Anselm Williams said the assault outside the fundraising dance at a New Brighton hall at about 1.30am was a deliberate act, without provocation, on a completely vulnerable victim.
It could not be categorised as a one-punch manslaughter case, Mr Williams argued.
He said that since Faletolu ran at the victim, and used his knee to assault him was very different to a "punch in anger".
Defence counsel Bridget Ayrey, however, said it was a "classic one strike manslaughter, and it should be treated as such".
It was not a concerted street attack, she said, rather a "fleeting and extremely reckless act" that has had such tragic consequences.
Faletolu had demonstrated genuine remorse, and had a bright future in front of him, Ms Ayrey said.
Justice Rachel Dunningham said Faletolu was a first time offender, who had a job, was involved in his church, had a girlfriend, and lived in a "warm, supportive family environment".