Mujahid Arshid has been found guilty of murdering his niece Celine Dookhran and the attempted murder of another woman.
Arshid, 33, was also found guilty of the rape and kidnap of 20-year-old Ms Dookhran, and the rape and kidnap of the other woman.
He was also found guilty of sexually assaulting the surviving victim when she was 13.
The jury deliberated for 14 hours before delivering the guilty verdicts.
Ms Dookhran’s family shouted “yes” when the verdict was returned.
Arshid ranted in the dock, claiming the surviving woman had “lied”.
The court heard throughout the course of the trial that Arshid had kidnapped the two women while wearing pyjamas and a balaclava.
He was said to have become “sexually fixated” with his niece, who worked in a Barclay’s bank.
He enlisted the help of Vincent Tappu, a labourer, to take the two women to a house between Kingston and Wimbledon in south west London, which they were helping to renovate.
They were bound and gagged, and when they arrived, they had their throats slit and were raped.
Prosecutors told the court Arshid was acting out sexual fantasies during the kidnap.
The second woman, who cannot be named for legal reasons, escaped when she convinced her attacker that they could be together.
The woman managed to raise the alarm and was rescued by Arshid’s brother, who saw her in the back of his truck and took her to St George’s Hospital in Tooting, where she went on to have two operations as she recovered from knife wounds.
In her hospital bed, she told police officers they would find Ms Dookhran’s body in the chest freezer.
“He brought Celine down in a bag, picked her up and put her into the chest freezer,” she told officers.
“All I could see was her legs sticking out. I had to act like it was not affecting me.”
She told the court the “psycho” builder had told her she had “10 minutes to live” after killing her friend.
When Arshid’s wife demanded to know where their niece was on WhatsApp, Arshid initially told her: “How do I know. She’s the one that ran off.”
She replied: “You would stoop that low. You’re the p***y.”
Arshid then said: “Whatever I may be, you made me. I’ll call you from Pakistan.”
But when his wife told him not to and that he was “dead to me”, he retorted: “So is Celine apparently.”
Arshid was arrested at a Holiday Inn in Folkestone.