Adele Bellis, then 22, lost an ear, is now partially bald and was left with "life-changing" permanent scarring.
The attack, at a bus stop in Lowestoft, Suffolk, on 14 August 2014, was ordered by her ex-boyfriend Anthony Riley, 27, Ipswich Crown Court was told.
Jason Harrison, 39, from Lowestoft, admits the attack and said Mr Riley promised to reduce a drugs debt.
Mr Riley, of Raglan Street, Lowestoft, denies false imprisonment, conspiracy to apply a corrosive liquid and conspiracy to cause GBH with intent.
Harrison claims a "jealous" Mr Riley recruited him as part of a campaign to "humiliate and control" his partner of nearly seven years.
But he had been reluctant to go through with the attack until Mr Riley threatened to harm him, his girlfriend and family, he said.
He owed Mr Riley Â£10,000 and would be let off some of it if he carried out the attack, he said.
Mr Riley told him where she lived and gave him Â£500 and a coffee jar containing sulphuric acid, the jury was told.
He aborted two attacks causing Mr Riley to punch him and put a knife in his mouth, Mr Harrison said.
"I didn't want to do this attack. I'm not a violent person," he said.
Prosecutor Andrew Jackson had earlier told the court Mr Riley arranged for co-defendant Leon Thompson, 39, to stab Miss Bellis in the face and posted a revenge porn sex video on Facebook.
Mr Thompson, 39, of Alma Road, Lowestoft, denies wounding with intent, having a knife in public, conspiracy to apply a corrosive liquid and conspiracy to cause grievous bodily harm with intent.
The trial continues
A man threw acid in a beautician's face because he feared for his life, family and girlfriend, a court has heard.