Sickening new video shows the moment the crazed career criminal charged in the fatal Brooklyn subway beatdown stomps on the helpless victim at least a dozen times — to the point that he knocks him unconscious.

Victim Nicola Tanzi, 64, stood no chance against David Mazariegos, who allegedly is seen in the disturbing clip entering the Jay Street-MetroTech station on Tuesday and immediately sucker-punching the Italian immigrant twice in the face, knocking him to the floor.

Mazariego, who has five open criminal cases, then continues his merciless assault — kicking Tanzi in the face over and over again while he’s on the ground, the video shows.

The creep later told cops he took Tanzi’s “spirit” because he didn’t like the way he looked at him, according to prosecutors.

The unprovoked attack occurred right after Tanzi held the emergency door open for Mazariegos.

“He then proceeded to stomp on the victim not once, not twice, but over and over and over again, even while the victim’s body was totally limp,” Assistant District Attorney Shena Aishnani said last week at the suspect’s arraignment. “The victim was completely unconscious and yet the defendant continued to stomp on his body.”

Aishnani added, “Police interviewed the defendant and he confessed to beating the victim, robbing him and taking his spirit, as he put it.”

Mazariegos is charged with first-degree murder in the chilling attack.

Prosecutors said Tanzi, a devout Catholic and member of the Italian club in Carroll Gardens, suffered skull fractures, a crushed nasal bone and several facial injuries — and died just a few hours later.

The Italian-born victim was a parishioner at St. Dominic’s parish, his family said.

“Nicky had such a kind heart and was always a glass-is-half-full kind of person and he always had concerns for others,” said John Heyer, the deacon of Sacred Hearts & St. Stephen Roman Catholic Church in Carroll Gardens.

“So, I believe he’d help and forgive the person who did this and [would have] gotten them the help that they needed.”

Mazariegos was busted after the attack and bizarrely flashed a toothless grin at reporters before he was charged and ordered held at Rikers Island without bail.

Records show he has five open cases in Manhattan and the Bronx, including for petty larceny, identity theft, criminal mischief and assault.