A martial arts expert at a Kent jail nicknamed "Stabside" threw a kettle of boiling water over a rival inmate.
Cagefighter Frank Ball claimed he was told there was a bounty on his head after being sent to HMP Swaleside, where 497 secret weapons were located in one year.
The attack was caught on prison CCTV which showed how fellow prisoner Thomas Lee was badly scalded in front of horrified inmates and staff.
Ball, from Perry Hill, Cliffe appeared in the dock at Maidstone Crown Court in handcuffs with three security officials by his side.
The court heard that arriving for his sentencing hearing the 32-year-old had told staff he was "going to kick off" in the dock.
Judge Tony Baumgartner told him it had been an horrific attack and Mr Lee "must have been terrified".
Bridget Todd, prosecuting, told how Ball had been serving a 10-years and four-month jail term when the attack happened.
He fled Medway Magistrates Court after assaulting a female guard, who was left with a broken pelvis.
The boxer also threatened children during the daring escape, in which Gillian Gray, 57, was seriously hurt.
Ms Todd said that in April 2018, he was in his cell at Swaleside when he asked an officer to open his door so he could associate with other inmates.
But minutes later, he was spotted running towards Mr Lee holding a white kettle with boiling water which he threw over the victim.
She said Mr Lee, who was scalded in the vicious attack, was urged to pour cold water over his face as Ball was ordered back to his cell.
Emin Kandola, defending, said Ball was held on a wing at Swaleside - nicknamed "Stabside" because of the number of stabbings.
She said that in one year, officials had found 497 hidden weapons.
"There was a bounty on the head of Mr Ball as a result of a robbery he had been convicted for."
She added Mr Lee had earlier attacked him and on this day he saw his rival walking towards his cell.
The barrister said Ball thought Lee might have a knife and was going to stab him and as he was boiling a kettle he used it as a weapon.
Ball - who has since been moved to another prison - was given an extra 20 months in prison after pleading guilty to assaulting causing actual bodily harm.
The judge told him: "It must have been a horrible thing for Mr Lee to have endured."