A cyber-bully eyeglass seller with an admittedly “big mouth” realized yesterday that he bit off more than he could chew when he viciously went after unhappy clients online.

Vitaly Borker shook his head in disbelief as he was hit with four years in the slammer for threatening to rape and murder women who complained about getting ripped off by his online business.

“You didn’t actually put a knife to someone’s throat, but you got the satisfaction that they felt you would,” Manhattan federal Judge Richard Sullivan said.

The punishment is nine months more than the maximum Borker had faced before challenging claims that he threatened to settle his customers’ grievances with violent, sexual revenge.

Sullivan said Borker’s “adamant” denials were proven false when five women testified against him in May and deprived him of any credit for pleading guilty in the case last year.

He also ordered Borker, 36, to pay a $50,000 fine and repay more than $46,000 he scammed from customers of DecorMyEyes.com.

Earlier, Borker, of Brooklyn, pleaded for mercy, insisting that he’s “genuinely and deeply sorry” and “never intended to carry out any of the threats.”

“I had a big mouth I just couldn’t control, and it ruined my life,” he said.

Borker also choked up as he described how his father died while he was out on bail, disgraced at the shame on their family.

Victim Clarabelle Rodriguez of Manhattan, who blew the whistle on Borker’s shady practices, attended his sentencing but didn’t speak in court.

Afterward, she said she had expected an even harsher sentence but was “glad it’s over.”

Rodriguez, who got duped into paying $486 for a pair of counterfeit Lafont sunglasses, also said she was “sticking to cheap sunglasses from now on” — and noted that she paid just $3.99 for the oversize Old Navy shades she was sporting yesterday.

Defense lawyer Dominic Amorosa denounced Borker’s sentencing as “a revenge proceeding” and vowed to appeal.