A man was lured to Stanwick Lakes and slashed repeatedly with a machete as he tried to run from his attackers, a court heard.
The two offenders sought to "exact their revenge" on the victim after he sold them £180 worth of cannabis - which they soon realised was just a bag of grass clippings.
His Honour Judge Timothy Smith said: "This was a premeditated, preplanned, cold and calculated attack to execute your revenge. And this very well could have been an execution."
Jason Grant, 24, of Kings Road, Rushden, and Jordan Matthews, 20, of Adnitt Road, Rushden, pleaded guilty to grievous bodily harm.
After the victim duped the two into buying the bag of grass, they sent a series of threatening messages to the victim's mother and brother, telling them he had messed 'with the wrong people'.
One message read: "Pay tonight or I pass the debt on.
"Face me or it's family and I ain't coming alone."
Then, on December 14, 2016, they arranged for a girl, who was a mutual friend of the victim, to meet him outside a supermarket and lure him to Stanwick Lakes.
Judge Smith said: "As the victim went down that dark, long drive to the park, he was unaware that [Grant and Matthews] were following in a car armed with a hunting knife and a machete."
The pair sprung on the victim in the park. As he tried to run Grant, wielding the machete, struck him once in the back and then in the shoulder with such force it broke the bones.
The victim said the second swing 'missed his head by inches'.
The victim ran to the park entrance but collapsed against a fence following another blow from the machete.
Judge Smith said: "You had him up against the fence. You, Grant, held the machete to his face and cut him near his eye. You, Matthews, drew a serrated hunting knife and stabbed him in the bicep.
"If not then for the sudden intervention of a member of the public who pulled up in a car, prompting you two to run away, this attack would have continued.
"It was a frenzied attack. The victim is fortunate that his injuries did not take his life, but they will have lasting consequences."
The victim needed 11 stitches to his face, 12 stitches to his bicep and extensive surgery to his shoulder.
Judge Smith, addressing the two in court, said: “You say you feel remorse for your actions, but I find it hard to ignore that during the victim impact statement, you found it appropriate to smile. It is not a smiling matter.”
Since his arrest, Grant has been treated for paranoid schizophrenia.
Both Grant and Matthews were sentenced to eight years in prison, which Judge Smith said was ‘the minimum sentence I can pass’.
DC Katy Tyrrell, from Wellingborough CID, said after the case: “This attack involved a machete and hunting knife and caused life-changing injuries to the victim.
“I am pleased that the offenders have been brought to justice and would like to thank everyone involved in this investigation.”