One of 59-year-old terminally ill Harry Wood's victims told him "you are going to hell" when he was sentenced on May 17 2018.
Wood, previously of Borrowdale Terrace, Seacroft, Leeds was found collapsed on the floor of his cell at HMP Leeds after falling out of his bed on the morning of May 27, an inquest at Wakefield was told.
An ambulance was called and Wood was taken to St James's Hospital, where he was pronounced dead just before 10pm that night.
The inquest heard a post mortem revealed he had suffered heart failure due to heart disease.
Leeds Crown Court was told Wood subjected his young victims to rape and other violent sex offences committed when he was aged between 11 and 40-years-old.
Wood admitted 38 offences against victims aged between two and 17-years-old.
Wood was suffering from chronic obstructive pulmonary disorder in his remaining lung.
The inquest heard Wood's health deteriorated after he was arrested in June 2017 on suspicion of child sex offences and remanded to Armley Prison.
Area coroner Jonathan Leach said while on remand Wood was told the cancer had returned and that he was dying.
Mr Leach said: "In April (2018) he spent a week in a hospice. Clearly there was an expectation his life would end at that stage.
Recording a verdict of death by natural causes, Mr Leach said: "He appeared to have rallied and returned to HMP Leeds.
"On May 27 he was found collapsed on the floor and taken to St James's Hospital, where notwithstanding treatment, death was confirmed at 9.51pm.
"At the sentencing hearing on May 17 2018, his victims, all now adults, wept as the court heard how they had suffered a lifetime of torment as a result of Wood's offending. Two of the women addressed Wood personally and read out their victim statements in court.
One said: "You ruined my childhood.
"All you care about is yourself. You put me through so much pain.
"You are going to hell, and believe me, the devil is going to be waiting there for you."
Another victim said: "I do not hate you. Only God can judge a person.
"I am reading this to give you an understanding of how this has affected me growing up."
Prosecutor David Hall also read statements on behalf of other victims.
One statement read: "This man made me suffer. I hope he suffers for the rest of his life in prison - because he is a monster."
The women described suffering from depression and anxiety for years after being targeted by Wood.
Wood was on trial in December 2017 facing further charges in addition to the offences he pleaded guilty to.
The trail had to be abandoned after he became ill.
Wood also threatened to harm victims' relatives if they ever told anyone about the abuse.
Many of the attacks carried out by Wood would have been regarded as rape offences under modern legislation.
Wood pleaded guilty to a total of seven offences of rape, three of attempted rape, four of gross indecency with a child, one of attempted buggery and 23 indecent assaults.
Sentencing Wood, judge Christopher Batty said: "The selfishness of people like you is quite breathtaking.
"Life revolves around your sexual gratification and you are prepared to use anyone to satisfy your needs, with a callous disregard for the consequences upon their lives."