Craig Robins was 27 when he was attacked, in Lomax Road, in Hednesford, on October 30, 2006. He was left brain damaged and he later died in 2019, aged 40.
James Milligan has now admitted the manslaughter of Mr Robins, while Gavin Brown has previously pleaded guilty to murder.
Bernie Peter Smith and Kyle Neil Smith have pleaded not guilty to manslaughter.
A trial at Stafford Crown Court was told that the co-defendants were part of a group involved in the incident during which the victim was stabbed, punched and kicked.
Prosecuting barrister Mr Jeremy Benson QC said: "On March 3, 2019 Craig Robins died as a result of sepsis or blood poisoning due to an incident. He was in a coma since October 30, 2006 some 12 and a half years before.
"The reason he was in a coma was a result of head injuries he has suffered when he was attacked in his car by these two defendants and two other men James Milligan and Gavin Brown.
"The result of the attack was a severe loss of blood leading to irreversible brain damage. After a long stay in hospital he was cared for by his family at home 24 hours a day. He never regained consciousness.
"There is no dispute in this case that his death in 2019 was directly caused by the devastating brain injury that was caused to him in 2006.
"This was not the first time that he had suffered serious injuries. In 1997 when he was 19 he was involved in a serious car accident which left him paralysed from the chest down," Mr Benson said.
He told the jury that Mr Robins, a jeweller, had the full use of his arms and an adaptable car.
He said that on October 30 he reported to police that the vehicle's tyre had been slashed while parked on the drive of his Hednesford home and on another occasion it was broken into.
Mr Benson said: "He suspected that he was being targeted because he was disabled."
He told the jury that on that evening Mr Robins decided to go out to find those responsible.
"It was believed that he unfortunately the he took a machete with him. He drove round the Hednesford estate and was making inquiries," he said.
Mr Benson said Bernie Smith and Kyle Smith were at a party at a property, in Lomax Road. Bernie Smith was outside and went indoors to tell his older bother Kyle that "someone in a silver car" threatened him.
"The four men went outside confronted and attacked Mr Robins as he sat in the drivers' seat. Gavin Brown grabbed the machete and dealt nine blows around his head and neck. The prosecution say Kyle Smith punched and kicked him. Gavin Brown picked up a brick and threw it through the drivers' window and that Bernie Smith kicked out at Mr Robins.
"The defendants then ran off."
Gavin Brown, 36, of HMP Lancaster Farm, pleaded guilty to murdering Mr Robins at a previous hearing. James Ainsley Milligan, 42, of Hednesford Road, Cannock, pleaded guilty to his manslaughter.
They will be sentenced at a later date.
Bernie Smith, 30, of Rowley Close, in Hednesford, and Kyle Smith, 33, of Pebble Mill Drive, Cannock, both deny manslaughter.
The trial continues.