A judge spoke of the “depressing” state of knife crime in London as two teenagers were found guilty of a machete attack.
Douglas Sepouo was set upon in Preston Park, Wembley, in front of families with children on 9 July last year.
The 21-year-old has been left in a permanent vegetative state, the Old Bailey heard.
Keiano Gooden-Josephs, 19, of Harrow Road, Wembley, and a 17-year-old boy will be sentenced on 28 February.
They were both cleared of attempted murder, but found guilty of wounding with intent, and Gooden-Josephs was found guilty of having a machete.
‘Left for dead’
Earlier in the trial, prosecutor Alistair Richardson described how the victim had screamed and tried to fend off his attackers.
He said: “Having followed Douglas Sepouo, they attacked him as he desperately tried to defend himself and screamed for help.
“Together, they hacked at him, one of them stabbing him in the chest with a machete. He was stabbed a number of times.
“When members of the public intervened, both ran off, disposing of their weapons as they fled. They left Douglas Sepouo for dead.
“His injuries were devastating, and he is unlikely to ever recover,” said Mr Richardson.
Judge Sarah Munro QC told jurors she often dealt with young men convicted of knife crimes.
She said: “We try to do everything we can to stop these offences. It gives nobody any pleasure.
“Only this morning, I have just dealt with a drug dealer who has himself been stabbed as a result of turf war but will not co-operate with police.
“I am dealing with another man in possession of a samurai sword and lock knife. That is just today in this court. It’s very depressing.”