He pummeled a 69-year-old man to his deathbed, yet Branlee Gonzalez — 19 at the time of the crime — was set to get no prison time and a clean adult record, thanks to Manhattan Judge Guy Mitchell.

But Mitchell blinked after The Post got on the story . To the defense’s consternation, the judge in court Monday stuck with his offer of “youthful offender” status — but said he’d impose a sentence of 1 ¹/₃ to four years in prison if Gonzalez pleaded guilty to first-degree manslaughter. That would mean he could be out in nine months.

Youthful offender status leaves the perp with no criminal record, so he needn’t reveal a conviction on work or college applications and can even hold public office.

Court records show the judge (a de Blasio appointee) in June indicated he was leaning to the no-prison sentence and bought Gonzalez’s claim to be done with gang membership. (He’s reputedly a “Gorilla Stones” associate.)

Note that Gonzalez actually beat two men in that 3:30 a.m. assault on Sherman Avenue in Inwood, though his 39-year-old victim suffered less-serious injuries. What set him off? Catcalls at his cousin.

And while Gonzalez turned himself in a few days after the attack, it was also after video of the crime had gone viral and was likely to get him caught anyway.

Mercy certainly has its place in court, but so does justice — including justice for Lucio Bravo, who died five days after the beating.

Which should require something a lot closer to what Assistant District Attorney Sarah Marquez asked for: at least 10 years behind bars, plus five years’ probation.

Empire State law has been turning markedly softer on younger criminals, driven in part by Assembly Speaker Carl Heastie’s theories that under-21s’ brains are still developing. Even so, Judge Mitchell seems bent on setting a new low.