An 18-month-old girl murdered by her guardian was "almost invisible to professionals" after she was taken into the care of the woman who would ultimately kill her.
Keegan Downer was killed by Kandyce Downer, 34, less than a year after she was appointed her legal guardian.
The toddler had 153 scars and bruises suffered due to "barbaric and evil" treatment, West Midlands Police said.
A serious case review found her death could not have been predicted.
But the report published on Wednesday said it found the assaults inflicted on Keegan may have been prevented by more professional involvement and supervision of Downer and her children.
Keegan, also known as Shi-Anne, died on 5 September 2015.
She was placed in foster care from an early age after being born in March 2014 to a heroin addict.
However, a guardianship order was granted to mother-of-four Downer in January 2015, and Keegan lived at Downer's family home in Beckbury Road, Weoley Castle, Birmingham.
The Birmingham Safeguarding Children Board report found that "very little" was known of what life was like for Keegan after she was placed with Downer.
"After the SGO [special guardianship order] was granted Shi-Anne was almost invisible to professionals," the report said.
She was not seen by any health, care or social services experts in the three months before her death.
The review found Keegan "should never have been placed" with Downer due to her "not really fitting the criteria to be awarded an SGO" and "the flawed and incomplete assessments".
The report adds: "The review author is firmly of the opinion that if an SGO was going to be awarded in this case (which he doesn't believe it should have been, as it neither met the original purpose or even the spirit of why SGO's were introduced) that a supervision order should have been attached to it."
Special guardianship orders have been reviewed by the government in the wake of this case and others, the review said.
Analysis - Harvey Gallagher, chief executive of the National Association of Fostering Providers
We've had growing concerns for a number of years about the assessment and choice of individuals who choose to apply (for SGOs).
There's a perception that the standards of assessment are not as high as they would be for foster carers. There should be high standards across the board.
The government did try to address this issue and made some tweaks to the system, which is welcome. Time will tell if those changes prove to be significant.
As for foster carers being taken seriously - the feeling is probably that they are not treated on the same level as professionals; that they are not valued in the same way. They are often not included in conversations about what should happen (to the child). They should be. Who knows the child better?
The review author also met with the foster mother who took care of Keegan for the first 10 months of her life.
The report says the foster carer, who says she was not contacted when Keegan was murdered, told a social worker she had "concerns" about Downer and her "motivation and how she was going to care for Shi-Anne didn't add up".
Meanwhile, the vetting process for Downer was "overlooked for seven weeks" while a social worker was off ill.
Birmingham City Council's children's services department took on an independent agency, called Minster Social Work Ltd, to assess whether Downer would be an appropriate guardian.
The allocated social worker was off sick for seven weeks and there were "important messages sent via email that were not read", the review found.
No-one else did any work on the case and three other social workers "knew nothing about it" despite being allocated it, the report said.
Despite this, the private firm returned a "positive assessment" of Downer's suitability to be the child's guardian.
Peter Hay, director of the council's children's services, said people had lost their jobs in the wake of the case.
"Employment action has been taken, including to the regulator. Those people are no longer working with us," he said.
Penny Thompson CBE, independent chair of the Birmingham Safeguarding Children Board said: "There was a superficial assessment by an external agency commissioned by the city council; little challenge on behalf of Shi-Anne and her lifelong interests; poor information exchange; insufficient discussion between involved agencies, and too much focus on Kandyce Downer's wants rather than the child's needs."
Downer was jailed for life in May 2016. She must serve at least 18 years behind bars.
An NSPCC spokesman said: "It is clear that the process of making Kandyce Downer responsible for Shi-Anne via a special guardianship order was deeply flawed, with a disturbing lack of assessment and scrutiny."
The city council's children's services is being taken over by a trust following years of failings.