The couple paid Waring $400 for cannabis but he failed to deliver the goods.
When the pair set up another meeting using a pseudonym, they were bent on violent retribution and exacted their revenge.
Therle was sentenced to seven months' home detention on counts of attempted kidnapping and assault with intent to injure while his girlfriend was ordered to complete 100 hours' community work for assault.
For his trouble, Waring was sentenced in December 2018 to three months community detention and 12 months' intensive supervision for offering to supply cannabis and an unrelated burglary.
A year later he was selling drugs again, the court heard this week.
Police searched his home after receiving reports of a robbery there.
They found pipes, 86g of dried cannabis leaf packaged in $25, $50 and $100 bags, along with tick lists and electronic scales — "the classic indices of drug dealing", Judge Peter Rollo said.
Waring admitted the dealing had gone on for eight months and he had made about $10,000 in sales.
Defence counsel Steve Turner said it was only $1250 a month and was done simply to feed the defendant's addiction to the drug.
A drug-and-alcohol report was "startling", Mr Turner said.
Waring, it revealed, had become a daily cannabis user at 14 and had also abused methamphetamine from an early age.
His addiction was assessed as severe but he was seen as motivated to address it.
Turner accepted the charges from 2018 were problematic but put it down to Waring being a "wise guy" at the time.
Judge Rollo said it was unfortunate the defendant had not learned from his first appearance in court but acknowledged it took young men some years understand the gravity of their decisions.
He said Waring was "academically gifted" and had strong family support.
The judge sentenced him to 15 months' intensive supervision and 250 hours' community work.
He also ordered judicial monitoring, meaning he would receive three-monthly reports about Waring's progress.
"I expect to see very positive reports about you turning your life around," Judge Rollo said.