The witness, codenamed Person 14, finished giving evidence on Thursday after four days of cross-examination where he was accused of lying and fabricating much of his story.
Mr Roberts-Smith's lawyer queried discrepancies between Person 14's testimony in the Federal Court and notes taken by Walkley Award-winning journalist Chris Masters of their February 2018 meeting.
"You say that (Mr Roberts-Smith) tended to go off and do things away from the rest of us," Arthur Moses SC read out from Masters' notes.
"Yes," Witness 14 replied.
"And did you say, things as time went on, the Colonel Kurtz Apocalypse Now factor took hold?"
"No."
"Did you say Mr Roberts-Smith had gone up the river ... Did you say that no one was stopping him, 'even though we saw it coming'?"
"No ... Mr Moses I did not."
"What Mr Masters has written and what I've said are two different things," he said, adding some of the notes were inaccurate.
Australia's most decorated living soldier is suing The Age, The Sydney Morning Herald and The Canberra Times, denying their reports that he committed war crimes and murders in Afghanistan between 2006 and 2012.
Person 14 also denied he cared that Mr Roberts-Smith was awarded the rare Victoria Cross medal in 2011 for "most conspicuous gallantry" in Afghanistan.
"You told Mr Masters you had doubts about the Victoria Cross?" Mr Moses said.
"I never mentioned anything about medals, medallic recognition, nothing," Person 14 said.
"You have been jealous about the fact that Mr Roberts-Smith was awarded the Victoria Cross?"
"No I wasn't there to make any comment on that."
Person 14 last week alleged he saw the VC recipient walk up to an interpreter telling him to order an Afghan soldier to shoot a detainee "or I will" towards the end of the mission in Khaz Uruzgan in 2012.
The witness also alleged he witnessed the infamous shooting of an unarmed Afghan man who had a prosthetic leg outside a Taliban compound dubbed Whiskey 108.
While his vision was not clear he did see the shooter holding a FN Minimi automatic gun, one he said on Thursday a junior soldier would normally carry.
He denied telling the journalist it had been the junior soldier who shot the Afghan, and maintained he later found out it was Mr Roberts-Smith and said so.
"You are a liar, aren't you?" Mr Moses said.
"No."
Earlier he was accused of making up a conversation with the war hero about an alleged war crime in which Mr Roberts-Smith said "it's your word against" another colleague.
Person 14 says Mr Roberts-Smith said "oh, so it's going to be like that, is it?".
In the marquee defamation trial Mr Roberts-Smith denies all wrongdoing and says he acted within the moral and legal rules of military engagement during his six tours of Afghanistan between 2006 and 2012.
The Age, The Sydney Morning Herald and The Canberra Times have pleaded a truth defence.
The third Australian witness - Person 16 - to be called by the newspapers is due to begin giving evidence on Friday.
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