Developer Mr Tom Gilmartin was a "spiteful, vindictive and ungrateful man," his business rival, Mr Owen O'Callaghan, has told the tribunal.
Mr Gilmartin "upset" the entire development plan for west Dublin with his proposal for a massive shopping centre at Quarryvale, Mr O'Callaghan claimed.
Mr O'Callaghan said his plans for a rival centre at nearby Balgaddy were "completely destroyed" by Mr Gilmartin's insistence on getting Quarryvale off the ground, "even though he didn't know what he was at".
The supermarket chains that were the main prospective tenants of a shopping centre would never have gone to Balgaddy when a better site was available at Quarryvale, he said. If Quarryvale had not been developed (by Mr O'Callaghan ultimately, as the Liffey Valley centre), Balgaddy would be doing "almost as much" business as the Liffey Valley centre is today.
Answering questions from former TD Mr Liam Lawlor, Mr O'Callaghan said it was "ridiculous" for Mr Gilmartin to suggest he had "pulled a stunt" by applying for planning permission for Balgaddy.
As for Mr Gilmartin's claim that Mr O'Callaghan, acting in a conspiracy with the banks, had defrauded him, this was "completely untrue," the witness said.
Mr O'Callaghan said he had treated Mr Gilmartin in an extremely fair way but felt he had been badly treated.
Mr Lawlor pointed out that Mr Gilmartin, in his evidence, had referred to Mr O'Callaghan as a "crook, a gangster and a cuckoo".
Mr O'Callaghan said these were "outrageous lies". While he would prefer not to elaborate, he felt he could call Mr Gilmartin a lot worse things than a cuckoo.
Mr Lawlor suggested that Mr Gilmartin was "a magpie" and "a scavenger" and Mr O'Callaghan agreed.
There were several reasons he had got involved in business with Mr Gilmartin, he said. One was that Mr Gilmartin owed him £1.3 million, which was the outstanding payment due on the co-operation agreement the two men had signed. "If Tom had paid us the money, we wouldn't be here today."
Also, he was anxious to get a development going in Dublin. He was fronting a company with 400 or 500 people, whereas Mr Gilmartin was "going around on his own with a briefcase".
At the time, Mr O'Callaghan conceded, he was "going nowhere". His plans for a town centre at Cooldrinagh has failed and Mr Gilmartin had "killed off" Balgaddy. His banks suggested he go into business with Mr Gilmartin at Quarryvale.
The witness rejected a claim by Mr Gilmartin that he had changed the text of the legal agreement between the two developers in his favour, saying this was "completely untrue" and a "terrible stigma" on the lawyers involved.
He also rejected Mr Gilmartin's claim to have introduced the Duke of Westminster to the Quarryvale project, "the most false claim" made by his rival.
The Duke of Westminster's companies and Mr O'Callaghan ultimately developed Quarryvale as the Liffey Valley centre.
Mr Gilmartin had completely ignored the development plan. "Anyone with any knowledge of planning would not have attempted what he attempted. It was extremely foolish and the size was way too big for Dublin." He said Quarryvale would still be limited to a size of 700,000 square feet in the year 2011, yet in 1988 Mr Gilmartin wanted to build a shopping centre with 1.5 million square feet of space.
