Amber Heard insulted Johnny Depp during a Christmas trip to the Bahamas, his estate manager has claimed.
Tara Roberts told London's High Court that Ms Heard, 34, called Mr Depp, 57, "washed up" and "fat".
Mr Depp is suing the publisher of the Sun over an article that labelled him a "wife beater" - but the newspaper insists it was accurate.
He denies 14 domestic violence allegations which News Group Newspapers is relying on in its defence.
In her witness statement at the High Court, Ms Roberts, who is the estate manager of Mr Depp's Caribbean home, claimed she had seen Ms Heard screaming at and berating the actor as he yelled at her to "go away".
Ms Roberts, who has worked for Mr Depp since December 2008, added that she saw a "red, swelling gash" on his nose, and that he had told her Ms Heard had thrown a can of lacquer thinner into his face.
She went on to describe Mr Depp as an "unusually kind man", saying she had never seen him be "violent or aggressive" with Ms Heard, or anyone else.
Ms Roberts alleged that she saw Ms Heard "lunge violently at Johnny, pull his hair, and commit other aggressive physical acts against him".
Ms Roberts said that on 29 December 2015, when the couple were staying on the island with his two children and a friend, the pair had an argument.
In her statement, she said: "While I could not hear what caused the fight, Amber repeatedly berated him with increasing ferocity.
"She was insulting him, calling him names, and in the middle of this onslaught I heard her say specifically 'your career is over', 'no one is going to hire you', 'you're washed up', 'fat', 'you will die a lonely man', and also screaming things that were incomprehensible."
Ms Roberts claimed Mr Depp tried to leave, repeatedly asking for the key to a vehicle, which Ms Heard refused to give back, adding it was later found in the couple's house.
She said during the entire incident, she "never saw" Mr Depp hit or push Ms Heard, and "nor did he physically react to the attacks".
She said on walking Mr Depp to a café later on, she saw he had "a red, swelling gash on the bridge of his nose".
"Amber, Johnny then told me, had thrown a quart sized can of lacquer thinner into Johnny's face, causing a gash," her witness statement said.
Ms Roberts claimed she did not see any signs of injury on Ms Heard's face or body during the trip.
Sasha Wass QC, representing Sun publisher News Group Newspapers, asked her about the former couple's Bahamas stay, and Ms Roberts said she was not aware their relationship was very difficult at that time.
Ms Wass said: "As far as you were concerned, you have suggested that it was Ms Heard who was the most violent, is that right?"
Ms Roberts replied: "Correct."
She was shown a photograph from around that time of Ms Heard with bruising on her face but said she had not seen this bruising when she saw the pair after the row.
During an exchange with Mr Depp's barrister David Sherborne, Ms Roberts said that she "never saw" the actor being violent or aggressive towards Ms Heard on the island.
Mr Sherborne asked the estate manager whether she was "lying" to protect Mr Depp because she was "worried" about losing her job. She replied that she was not.
Hollywood stylist Samantha McMillen told the court Ms Heard had "no visible" injuries the day after the actress alleges Mr Depp was violent towards her in a separate incident in late 2015.
Ms McMillen said she spent "much of the afternoon and early evening" with Ms Heard on 16 December 2015 as she prepared to appear on a US late-night talk show.
In a witness statement, Ms McMillen said she saw Ms Heard "in good light, at close range, wearing no make-up", adding: "I could see clearly that Ms Heard did not have any visible marks, bruises, cuts, or injuries to her face or any other part of her body."
The stylist said after the programme Ms Heard said to her: "Can you believe I just did that show with two black eyes?"
Ms McMillen said: "Ms Heard did not have any black eyes, and had been visibly uninjured throughout the day and at that moment."
The libel case arose out of the publication of an article on the Sun's website headlined: "Gone Potty: How can JK Rowling be 'genuinely happy' casting wife beater Johnny Depp in the new Fantastic Beasts film?".
The Sun's original article related to allegations made by the actress, who was married to the film star from 2015 to 2017.