A vulnerable man who was murdered by his ex-partner and her lover could have been better protected, a review found.
Phillip Nicholson, 22, died from a stab wound to the neck after being lured to a flat in Bournemouth in May 2015.
Isabella Gossling, 20, and her lover Richard Moors, 26, are both serving life sentences for the murder.
The combined safeguarding and homicide review revealed a catalogue of concerns involving the trio in the months leading up to Mr Nicholson's death.
It said Mr Nicholson had been in an on-off relationship with Gossling and was thought to be the father of her baby, despite her also being in a relationship with Moors.
Moors was described as a "predator" with a history of homelessness, gravitating towards vulnerable people with whom he would stay and "exploit for his personal advantage or gratification".
The review said individual agencies realised Moors was a risk to vulnerable people but a lack of information sharing prevented them fully understanding the threats he posed.
It said the care agency that helped Mr Nicholson live independently lodged concerns that Gossling was financially, physically and emotionally abusing him.
It also said Gossling, who had atypical autism, was also at "high risk" from domestic abuse from Moors.
The report said police failed to visit Moors after he and Gossling sent death threat texts to Mr Nicholson.
On 26 May 2015, Mr Nicholson, who had a learning disability, was lured to his death at Gossling's flat.
An audio recording of his murder was found on Gossling's phone.
She was jailed for a minimum of 19 years. Moors was jailed for a minimum of 22 years.
Barrie Crook, chairman of Bournemouth and Poole Safeguarding Adults Board, said: "Actions have been taken as a matter of priority to ensure that circumstances leading to deaths such as this are prevented from happening again in the future.
"There were key opportunities to intervene which seem likely to have afforded [Mr Nicholson] greater protection and may have restrained the behaviour of [Gossling] and [Moors] for a time."
In a statement, Mr Nicholson's family said: "Sadly and upsettingly, it has become evident throughout these investigations that significant failings and omissions were made by those organisations involved in Phillip's care which we strongly believe could have prevented his death.
"We support the findings of the report and the lessons that need to be learnt, but it provides us with no comfort having lost Phillip."