His plain pine coffin, which arrived at the church in a Rolls-Royce hearse, was draped with his court robe, wig and familiar blue bag.
The Wellington District Court, where Mr King spent much of his legal career, was closed so staff could pay their respects.
Mr King, who was 43, was described as someone who was dedicated to the law, passionate about representing the underdog, loyal to his family and friends and generous to a fault.
Mrs Milnes-King said the depth of her grief at losing her soulmate was like a "black hole".
"Upon receiving the news it plunged across the event horizon," she said. "You are my stars, you are my moons, you are my universe, you are my everything."
Mr King's father, Jeffrey King, said he could not remember his son making a poor choice until last Friday. "Thanks for being my son, Greg, you'd have had a wonderful party if you could see everyone here."
His mother Jennifer called him a wonderful son and said: "I am privileged to be his mother. Rest in peace, Gregory."
Judith Ablett-Kerr, QC, Mr King's mentor, said of her close friend: "His talents seemed to know no bounds and his energy was limitless as he searched for the stars. The light that burned so brightly was extinguished so sadly and unexpectedly."
Mr King, who successfully defended Ewen Macdonald on a charge of murdering his brother-in-law Scott Guy, seemed gifted at identifying with people associated with all aspects of the legal system, the service was told.
Justice William Young said Mr King was known for the empathy he felt for victims of crime. Crown prosecutor Simon Moore, SC, said Mr King was among the "giants of criminal law" and "scrupulously honest".
"If Greg said it was so, it was, because his word was his bond."
It was a tribute to Mr King that people from all aspects of the legal profession as well as victims of crime felt a keen loss at his death, he said.
Robert Lithgow, QC, said Mr King was admired among the legal fraternity because he always made an effort to help people who found themselves in a predicament.
"He was one of those lawyers who could find something good even in the most unsatisfactory of people."
Archdeacon Monty Black said Mr King had been exhausted, unwell and disillusioned.
Brooke Fraser, the daughter of Mr King's close friend and former All Black Bernie Fraser, sang at the service and screens displayed images of Mr King from throughout his life.
Mr King was born in Wanganui, raised in Turangi and studied law at Otago University. His death has been referred to the coroner.