A Manhattan judge today handed down the maximum sentence possible, 25 years to life, to Renato Seabra, the Portuguese underwear model convicted of brutally bludgeoning and castrating — with a corkscrew — his sugar daddy in their Times Square hotel room last year.

The no-mercy sentence came despite a plaintive, almost whispered request for forgiveness, in Portuguese, by Seabra himself, as the pale young man sat rear-cuffed and ringed by court officers in Manhattan Supreme Court.

“I just want to request the opportunity to ask for forgiveness to Carlos Castro’s family and friends,” he said softly, in the first remarks he has made publicly on the heartless murder.

The victim, a wealthy, widely published journalist on the topics of fashion, gossip and gay rights in his native country, was left splayed naked on the hotel room carpeting, his face an unrecognizable pulp from being stomped on and repeatedly slashed at with a cork screw.

The young gigolo — he was only 21 years at the time — had admitted ripping open the dying man’s scrotal sac with the same corkscrew, slitting his own wrists, and then applying the severed testicles to his own bleeding arms so he could “harness their power,” as he’d told shrinks. Jurors had rejected the defense claim that the attack was so out of character, and so bizarrely horrific, that Seabra must be found not guilty by reason of insanity.

“I also want to add that at the time when the crime happened, I wish to say I killed Carlos Castro,” Seabra continued, addressing Manhattan Supreme Court Justice Daniel FitzGerald without looking at him.

“That’s not anything I want to prove differently. At the moment I went into the room on that day,” he said of their room at the InterContinental, “something took power of me. We used it to fight each other but it was always playfully,” he said.

“I was never aggressive before. I never had any fight with Carlos.

“On that day I don’t know what took over me. I did not understand the manner — how things happened, and I could not understand why,” he said, sitting ringed by six court officers and still staring down at the table.”

“Finally, I want to once again to excuse myself to cc’s friends and family and I accept anytime the judge will tell me because I committed the crime and now only god knows what happened on that day.”

In rendering the severest sentence statutorily available, the judge noted the unfathomable heinousness of the crime.

“Here an argument escalated from anger to rage to really a chilling example of man’s inhumanity to man,” FitzGerald said. “There was extreme brutality, sadism and dehumanizing acts,” he said.

The violence came out of nowhere, noted defense lawyer David Touger.

“I don’t know how Renato committed this crime. It just doesn’t seem to be inside him,” the lawyer said, pointing to Seabra’s lack of psychiatric or criminal history prior to the attack.

“I don’t see that when I look in Renato’s eyes and I talk to people who have known him his entire life,” the lawyer said. “There is only one way Renato could have committed these acts and it is that he was in the throes of mental disease or defect.”

But prosecutor Maxine Rosenthal — who’d argued that the attack was fueled not by madness, but a clear-minded rage that the “gravy-train” relationship with his rich lover was ending — countered that Seabra was deceptive, manipulative and dangerous.

“Irrespective of any mental illness, this defendant has shown himself to be an angry man capable of extreme violence,” she told the judge in asking successfully for the max.

The sentence left Seabra’s mother in near hysterical tears, but was a comfort to Castro’s family.

Said family friend Monica Pires, “He needs to pay for what he did.”