He's no stranger to Victoria's courts either and says he'll cop to the things he's done, including fatally shooting "hothead" hitman Andrew 'Benji' Veniamin in self-defence.

But the 64-year-old is suing the ABC for defamation, arguing he was hurt and deeply aggrieved by accusations that went beyond what he's done.

"I'm hoping to cause them as much grief as they caused me," Mr Gatto told Victoria's Supreme Court on Wednesday.

Mr Gatto said he went into shock after reading the February 2019 article, which it's argued implied he was a hitman, a murderer, that he plotted to lure a man to his death and that he threatened to kill lawyer-turned-informer Nicola Gobbo.

"It refers to me as one of the most violent blokes in Australia," Mr Gatto said.

He said he initially asked the public broadcaster to remove the article and issue an apology and retraction, but they refused.

He's still asking for a public apology, but now also wants "the maximum payout I possibly can".

His barrister David Klempfner said the article's focus was on Mr Gatto's "propensity not only for violence but to orchestrate or make threats to kill".

He said it implied Mr Gatto was involved in the unsolved murder of fruiterer Frank Benvenuto in 2000 and of the murder of Victor Peirce in 2002.

"It's particularly harmful and hurtful for Mr Gatto because he has been accused of murder in the past ... and was acquitted," he said.

He spent 15 months behind bars awaiting trial for Veniamin's murder, before being acquitted.

The ABC's barrister Matt Collins said allegations Mr Gatto had been involved in the murders of Frank Benvenuto and Victor Peirce were made by a witness in criminal proceedings in 2008.

He has never been charged.

Claims he threatened to kill Ms Gobbo were made in a secret police witness statement, used in an effort by Victoria Police to keep her name protected.

It's argued the article is a fair and accurate report of court proceedings and the allegations in the article are protected.

Mr Gatto said on Wednesday that the witness, who cannot be identified, was a "puppet" for the police and the allegations weren't true.

He said Ms Gobbo's lawyers called him on Tuesday, saying she would give evidence that he had never threatened her.

Mr Gatto's lawyers have also accused the article's authors Nino Bucci and Sarah Farnsworth - who are also named in the defamation suit - of "editorialising and speculating" beyond providing fair court reports.

Mr Gatto will return to the witness box on Thursday.

Australian Associated Press