The now 43-year-old British national is set to be deported from Australia after being handed a suspended jail sentence.
He pleaded guilty in a Brisbane court on Friday to one count of supplying a dangerous drug and one count of possessing a dangerous drug.
The supply charge involved about 425kg of a substance containing about 300kg of MDMA, while the charge of possession related to 752kg of a crystallised substance that was about 71 per cent pure MDMA.
The drugs had a street value of about $823 million, prosecutor Sarah McFarland told the court.
In a moving confession, Cooper's stepfather took responsibility for normalising criminal behaviour and introducing his stepson to cocaine, Supreme Court Justice Peter Callaghan said.
Cooper regarded the man - who used drugs and alcohol heavily - to be his primary father figure from the age of about eight.
The stepfather and Cooper's mother spent time in custody during his childhood.
It was after the breakdown of a 10-year relationship and the sudden death of a family member that Cooper increasingly became drug addicted.
He accumulated a significant debt and was motivated by his supplier's threats to become involved in a syndicate which was what brought him to Australia.
"You did become a capable accomplice in a highly sophisticated operation … (that) involved moving an enormous quantity of a dangerous drug and the value was staggering," Justice Callaghan said.
Cooper was to benefit mostly from a waiver of his debt.
Justice Callaghan credited Cooper for "profound" rehabilitation while in custody since August 2019.
He sentenced Cooper to five years in jail, suspended immediately.
"The effect of the sentence … is to facilitate your deportation sooner rather than later," Justice Callaghan told Cooper.
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