The court heard how Ikamanu was looking after Seini and her younger brother on March 24, 2010, while Sela was at work.
Ikamanu was watching TV and Seini and her brother were playing noisily close by.
Justice Geoffrey Venning said Ikamanu asked the pair to stop.
"Seini ignored your request and just looked at you. She continued to run around and you became angry with her."
Ikamanu grabbed the 2-year-old and swung her in front of him before letting her go. "She was propelled into the wall."
But Ikamanu didn't stop there. He walked over to where Seini lay on the floor and stomped on her pelvis.
Seini was left with a fractured shoulder, shattered pelvis and head injuries that would prove fatal.
Ikamanu took her to the shower and tried to get her to drink water but the damage was done. Seini was having seizures.
Ambulance officers first on the scene told Ikamanu's trial the little girl "flopped like a rag doll".
Seini was rushed to hospital, where doctors later found bleeding in the left side of her skull which pushed her brain to one side of her head.
Only her brain stem was functioning and, despite surgery, she remained in a coma until her death eight months later.
Crown prosecutor Phil Hamlin had argued at trial that bruises found on Seini in the days leading up to the attack had been caused by Ikamanu, despite the girl telling her mother that she fell down the stairs.
But at sentencing yesterday, Justice Venning said he did not find the bruises were caused by Ikamanu and described his violent reaction as a "one-off" born out of frustration.
He took into account Ikamanu's remorse, the apology to his wife and family, his previous good record and the fact that he had offered to plead to the manslaughter charge before trial.
Ikamanu's lawyer, Simon Lance, said his client did not know his own strength but acknowledged he had caused the fatal head injuries.
Ikamanu still denies the stomping.
"He didn't mean to kill his daughter. He is very sorry for it and he has the full support of his family," Mr Lance said, referring to relatives in the public gallery.
He said Ikamanu was facing deportation to Tonga once he served his prison sentence.
Outside court yesterday, Sela Ikamanu held 4-month-old Cecilia and said she would trust her husband with their children in the future and had forgiven him for causing the fatal injuries to Seini.
Detective Sergeant Steve Brewer from the police child protection team said he understood how Sela's faith allowed her to forgive her husband.
"She's far more forgiving than I am or could ever be."
Starship hospital child protection clinical director Dr Patrick Kelly said his team saw head injuries caused by assaults on children and babies on average once a month. "It's from people losing it completely."
New Zealand has the OECD's fifth-highest rate for deaths from maltreatment of children under 15.