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 att

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